0,2

Number of nodes in rooted tree of height n in which every node (including the root) has valency 3.

Pascal diamond numbers : reflect Pascal's n-th triangle vertically and sum all elements. E.g. a(3)=1+(1+1)+(1+2+1)+(1+1)+1. - Paul Barry (pbarry(AT)wit.ie), Jun 23 2003

Number of 2 X n binary matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (00;1), (10;0), and (11;0). 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 and 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

J. Riordan, Series-parallel realization of the sum modulo 2 of n switching variables, in Claude Elwood Shannon: Collected Papers, edited by N. J. A. Sloane and A. D. Wyner, IEEE Press, NY, 1993, pp. 877-878.

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).

G.f.: (1+x)/(1-3*x+2*x^2). a(0)=1, a(n) = 2*{a(n-1) + 1}.

G.f. is equivalent to (1-2x-3x^2)/((1-x)(1-2x)(1-3x)). - Paul Barry (pbarry(AT)wit.ie), Apr 28 2004

A099257(a(n))=A099258(a(n))=a(n); a(n)=2*A055010(n)=(A068156(n)-1)/2. - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Oct 09 2004

Row sums of triangle A130452. - Gary W. Adamson (qntmpkt(AT)yahoo.com), May 26 2007

Row sums of triangle A131110. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Jun 15 2007

Binomial transform of (1, 3, 3, 3,...). - Gary W. Adamson (qntmpkt(AT)yahoo.com), Oct 17 2007

Binomial transform of [1, 3, 3, 3,...]. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Oct 21 2007

Row sums of triangle A051597 (a triangle generated from Pascal's rule given right and left borders = 1, 2, 3,...). - Gary W. Adamson (qntmpkt(AT)yahoo.com), Nov 04 2007

Equals A132776 * [1/1, 1/2, 1/3,...]. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Nov 16 2007

with (combinat):a:=n->stirling2(n, 2)+stirling2(n+1, 2): seq(a(n), n=1..28); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 07 2007

a[0]:=0:a[1]:=1:for n from 2 to 50 do a[n]:=(a[n-1]+1)*2 od: seq(a[n], n=1..28); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Feb 22 2008

Cf. A033484.

Cf. A131110.

Cf. A051597.

Cf. A132776.

Sequence in context: A038621 A078407 A099018 this_sequence A008267 A056112 A118430

Adjacent sequences: A033481 A033482 A033483 this_sequence A033485 A033486 A033487

nonn,easy

njas