0,3

Number of edges in n-dimensional hypercube.

Number of 132-avoiding permutations of [n+2] containing exactly one 123 pattern. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jul 13 2001

Number of ways to place n-1 nonattacking kings on a 2 X 2(n-1) chessboard for n >= 2 - Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), May 22 2001

Arithmetic derivative of 2^n: a(n) = A003415(A000079(n)). - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Feb 26 2002

(-1) times determinant of matrix A_{i,j} = -|i-j|, 0<=i,j<=n.

a(n)= number of ones in binary numbers 1 to 111...1 (n bits). a(n) = A000337(n)-A000337(n-1) for n = 2,3,... - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 24 2003

The number of 2 X n 0-1 matrices containing n+1 1's and having no zero row or column. The number of spanning trees of the complete bipartite graph K(2,n). This is the case m = 2 of K(m,n). See A072590. - W. Edwin Clark (eclark(AT)math.usf.edu), May 27 2003

Binomial transform of [0,1,2,3,4,5,...]. Without the initial 0, binomial transform of odd numbers.

With an additional leading zero, [0,0,1,4,...] this is the binomial transform of the integers repeated A004526. Its formula is then (2^n(n-1)+0^n)/4. - Paul Barry (pbarry(AT)wit.ie), May 20 2003

PSumSIGN transform of A053220. PSumSIGN transform is A045883. Binomial transform is A027471(n+1). - Michael Somos, Jul 10 2003

Number of zeros in all different (n+1)-bit integers. - Ralf Stephan (ralf(AT)ark.in-berlin.de), Aug 02 2003

Final element of a summation table (as opposed to a difference table) whose first row consists of integers 0 through n(or first n+1 nonnegative integers A001477);Illustrating the case n=5:

0...1...2...3...4...5

..1...3...5...7...9

....4...8...12..16

......12..20..28

........32..48

..........80, and final element is a(5)=80. - Lekraj Beedassy (blekraj(AT)yahoo.com), Jun 03 2004

This sequence and A001871 arise in counting ordered trees of height at most k where only the right-most branch at the root actually achieves this height and the count is by the number of edges, with k = 3 for this sequence and k = 4 for A001871.

Let R be a binary relation on the power set P(A) of a set A having n = |A| elements such that for all elements x,y of P(A), xRy if x is a proper subset of y and there are no z in P(A) such that x is a proper subset of z and z is a proper subset of y. Then a(n) = |R|. - Ross La Haye (rlahaye(AT)new.rr.com), Sep 21 2004

Number of 2 X n binary matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (00;1) and (10;1). An occurrence of a ranpp (xy;z) in a matrix A=(a(i,j)) is a triple (a(i1,j1), a(i1,j2), a(i2,j1)) where i1<i2, j1<j2, and these elements are in same relative order as those in the triple (x,y,z). - Sergey Kitaev (kitaev(AT)ms.uky.edu), Nov 11 2004

Number of subsequences 00 in all binary words of length n+1. Example: a(2)=4 because in 000,001,010,011,100,101,110,111 the sequence 00 occurs 4 times. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 04 2005

Let M=[1,i;i,1], i=sqrt(-1). Then g.f.=x/det(I-xM). - Paul Barry (pbarry(AT)wit.ie), Apr 27 2005

If you expand the n-factor expression (a+1)(b+1)(c+1)...(z+1), there are a(n) variables in the result. For example, the 3-factor expression (a+1)(b+1)(c+1) expands to abc+ab+ac+bc+a+b+c+1 with a(3) = 12 variables. - David W. Wilson (davidwwilson(AT)comcast.net), May 08 2005

An inverse Chebyshev transform of n^2, where g(x)->(1/sqrt(1-4x^2))g(xc(x^2)), c(x) the g.f. of A000108. - Paul Barry (pbarry(AT)wit.ie), May 13 2005

Sequences A018215 and A058962 interleaved. - Graeme McRae (g_m(AT)mcraefamily.com), Jul 12 2006

The number of never-decreasing positive integer sequences of length n with a maximum value of 2*n. - Ben Thurston (benthurston27(AT)yahoo.com), Nov 13 2006

Total size of all the subsets of an n-element set. For example, a 2-element set has 1 subset of size 0, 2 subsets of size 1, and 1 of size 2. - Ross La Haye (rlahaye(AT)new.rr.com), Dec 30 2006

Convolution of the natural numbers [A000027] and A045623 beginning [0,1,2,5...]. - Ross La Haye (rlahaye(AT)new.rr.com), Feb 03 2007

If M is the matrix (given by rows) [2,-1;0,2] then the sequence gives the (1,2) entry in M^n. - Antonio M. Oller (oller(AT)unizar.es), May 21 2007

If X_1,X_2,...,X_n is a partition of a 2n-set X into 2-blocks then, for n>0, a(n) is equal to the number of (n+1)-subsets of X intersecting each X_i (i=1,2,...,n). - Milan R. Janjic (agnus(AT)blic.net), Jul 21 2007

Number of n-permutations of 3 objects u,v,w, with repetition allowed, containing exactly one u. Example: a(2)=4 because we have uv, vu, uw, and wu. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 27 2007

A member of the family of sequences defined by a(n) = n*[c(1)*...c(r)]^(n-1); c(i) integer. This sequence has c(1)=2, A027471 has c(1)=3. - Ctibor O. ZIZKA (ctibor.zizka(AT)seznam.cz), Feb 23 2008

S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures}, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 796.

A. T. Benjamin and J. J. Quinn, Proofs that really count: the art of combinatorial proof, M.A.A. 2003, id. 131.

M. Elkadi and B. Mourrain, Symbolic-numeric methods for solving polynomial equations and applications, Chap 3. of A. Dickenstein and I. Z. Emiris, eds., Solving Polynomial Equations, Springer, 2005, pp. 126-168. See p. 152.

F. A. Haight, Overflow at a traffic light, Biometrika, 46 (1959), 420-424.

A. F. Horadam, Special properties of the sequence W_n(a,b; p,q), Fib. Quart., 5.5 (1967), 424-434. Case n->n+1, a=0,b=1; p=4, q=-4.

Jones, C. W.; Miller, J. C. P.; Conn, J. F. C.; Pankhurst, R. C.; Tables of Chebyshev polynomials. Proc. Roy. Soc. Edinburgh. Sect. A. 62, (1946). 187-203.

T. Y. Lam, On the diagonalization of quadratic forms, Math. Mag., 72 (1999), 231-235 (see page 234).

W. Lang, On polynomials related to powers of the generating function of Catalan's numbers, Fib. Quart. 38,5 (2000) 408-419; Eqs. (38) and (45), lhs, m=4.

Franklin T. Adams-Watters, Table of n, a(n) for n = 0..500

Milan Janjic, Two Enumerative Functions

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, December 1972 [alternative scanned copy].

S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures}, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.

S. Plouffe, 1031 Generating Functions and Conjectures, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.

D. W. Bass and I. H. Sudborough, Hamilton decompositions and (n/2)-factorizations of hypercubes, J Graph Algor. Appl. 7(2003) 79-98.

D. Callan, A recursive bijective approach to counting permutations...

P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

F. Ellermann, Illustration of binomial transforms

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 408

S. Kitaev, On multi-avoidance of right angled numbered polyomino patterns, Integers: Electronic Journal of Combinatorial Number Theory 4 (2004), A21, 20pp.

S. Kitaev, On multi-avoidance of right angled numbered polyomino patterns, University of Kentucky Research Reports (2004).

M. L. Perez et al., eds., Smarandache Notions Journal

A. Robertson, Permutations containing and avoiding 123 and 132 patterns

A. Robertson, H. S. Wilf and D. Zeilberger, Permutation patterns and continued fractions, Electr. J. Combin. 6, 1999, #R38.

Eric Weisstein's World of Mathematics, Hypercube

Eric Weisstein's World of Mathematics, Leibniz Harmonic Triangle

Thomas Wieder, The number of certain k-combinations of an n-set, Applied Mathematics Electronic Notes, vol. 8 (2008).

Index entries for sequences related to Chebyshev polynomials.

a(n) = sum(k=1, n, k*binomial(n, k)). - Benoit Cloitre (benoit7848c(AT)orange.fr), Dec 06 2002

E.g.f. xexp(2x) - Paul Barry (pbarry(AT)wit.ie), Apr 10 2003

G.f.: x/(1-2x)^2. a(n)=2a(n-1)+2^(n-1). a(2n)= n4^n, a(2n+1)= (2n+1)4^n.

Starting 1, 1, 4, 12, .. this is 0^n+n2^(n-1), the binomial transform of the 'pair-reversed' natural numbers A004442 - Paul Barry (pbarry(AT)wit.ie), Jul 24 2003

Convolution of [1, 2, 4, 8, ...] with itself. - Jon Perry (perry(AT)globalnet.co.uk), Aug 07 2003

The signed version of this sequence, n(-2)^(n-1), is the inverse binomial transform of n(-1)^(n-1) (alternating sign natural numbers). - Paul Barry (pbarry(AT)wit.ie), Aug 20 2003

a(n-1)=sum{k=0..n, 2^(n-k-1)C(n-k, k)C(1, (k+1)/2)(1-(-1)^k)/2}-0^n/4. - Paul Barry (pbarry(AT)wit.ie), Oct 15 2004

a(n)=sum{k=0..floor(n/2), binomial(n, k)(n-2k)^2}; - Paul Barry (pbarry(AT)wit.ie), May 13 2005

a(n+2) = A049611(n+2) - A001788(n). Floretion Algebra Multiplication Program, FAMP Code: 1vessum(pos)seq[A], 1vessum(neg)seq[A], and 1vessumseq[A] (= (a(n)) from 2nd term) with A = + .5'i + .5i' + .5'ij' + .5'ki' + 2e. Sumtype is set to: default (ver. f) - Creighton Dement (creighton.k.dement(AT)uni-oldenburg.de), Aug 02 2005

a(n)=n!sum{k=0..n, 1/((k - 1)!(n - k)!)} - Paul Barry (pbarry(AT)wit.ie), Mar 26 2003

a(n) = sum(binomial(n+1,j)*(n+1-j),j=0..n). - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 22 2006

a(n+1)=Sum_{k, 0<=k<=n}4^k*A109466(n,k) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 13 2006

Row sums of A130300 starting (1, 4, 12, 32,...). - Gary W. Adamson (qntmpkt(AT)yahoo.com), May 20 2007

Equals row sums of triangle A134083. Equals A002064(n) + (2^n - 1). - Gary W. Adamson (qntmpkt(AT)yahoo.com), Oct 07 2007

a(2)=4 since 2314, 2341,3124 and 4123 are the only 132-avoiding permutations of 1234 containing exactly one increasing subsequence of length 3.

spec := [S, {B=Set(Z, 0 <= card), S=Prod(Z, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..29); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 09 2006

a:=n->sum (2^(n-1), j=1..n): seq(a(n), n=0..29); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 27 2007

A001787:=1/(2*z-1)**2; [Conjectured by S. Plouffe in his 1992 dissertation.]

with (combinat): c := n -> stirling2(n, 2): b := n -> if n<2 then 1; else c(n)-c(n-1); fi: a := n -> add(b(i)*c(n-i), i=1..n-1): seq(a(n), n=2..31); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 10 2007

(PARI) a(n)=if(n<0, 0, n*2^(n-1))

Partial sums of A001792. Cf. A053109, A001788, A001789. A058922(n+1) = 4*A001787(n).

Row sums of triangle in A003506. Equals A090802(n, 1).

Cf. A000337, A130300, A134083, A002064.

Three other versions, essentially identical, are A085750, A097067, A118442.

Cf. A027471.

Adjacent sequences: A001784 A001785 A001786 this_sequence A001788 A001789 A001790

Sequence in context: A090634 A085750 A097067 this_sequence A118442 A038592 A048776

nonn,easy,nice

njas