Search: id:A001048
Results 1-1 of 1 results found.

%I A001048 M0890 N0337
%S A001048 2,3,8,30,144,840,5760,45360,403200,3991680,43545600,518918400,
%T A001048 6706022400,93405312000,1394852659200,22230464256000,376610217984000,
%U A001048 6758061133824000,128047474114560000,2554547108585472000
%N A001048 n! + (n-1)!.
%C A001048 Number of {12,12*,1*2,21,21*}-avoiding signed permutations in the hyperoctahedral 
               group.
%C A001048 a(n)=the hook product of the shape (n,1). - Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               May 13 2004
%C A001048 Contribution from Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Dec 
               01 2009: (Start)
%C A001048 (1+(x-1)*exp(x))/x = Sum_{k>=1} x^k/a(k).
%C A001048 Setting x=1 yields Sum_{k>=1} 1/a(k) = 1. (End)
%D A001048 Archimedeans Problems Drive, Eureka, 24 (1961), 20.
%D A001048 Biondi, E.; Divieti, L.; Guardabassi, G.; Counting paths, circuits, chains 
               and cycles in graphs: A unified approach. Canad. J. Math. 22 1970 
               22-35.
%D A001048 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001048 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A001048 T. D. Noe, <a href="b001048.txt">Table of n, a(n) for n=1..100</a>
%H A001048 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=97">
               Encyclopedia of Combinatorial Structures 97</a>
%H A001048 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=641">
               Encyclopedia of Combinatorial Structures 641</a>
%H A001048 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=101">
               Encyclopedia of Combinatorial Structures 101</a>
%H A001048 T. Mansour and J. West, <a href="http://arXiv.org/abs/math.CO/0207204">
               Avoiding 2-letter signed patterns</a>.
%H A001048 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               UniformSumDistribution.html">Uniform Sum Distribution</a>
%H A001048 <a href="Sindx_Fa.html#factorial">Index entries for sequences related 
               to factorial numbers</a>
%F A001048 a(n) = (n+1)(n-1)!.
%F A001048 E.g.f.: x/(1-x) - ln(1-x). - Ralf Stephan, Apr 11 2004
%F A001048 The sequence 1, 3, 8, ... has g.f. (1+x-x^2)/(1-x)^2 and a(n)=n!(n+2-0^n) 
               =n!A065475(n) (offset 0). - Paul Barry (pbarry(AT)wit.ie), May 14 
               2004
%F A001048 Factorial expansion of 1: 1 = sum(1/(n! + (n-1)!)) for n>0 = sum(n/(n 
               + 1)!) for n>0. 1 = 1/2 + 1/3 + 1/8 + 1/30 + 1/144 + 1/840 + 1/5760 
               + 1/45360 + 1/403200 + 1/3991680 + 1/43545600..... - Claude Lenormand 
               (claude.lenormand(AT)free.fr), Aug 24 2003
%F A001048 a(1)=2, a(2)=3, a(n)=(n^2-n-2)*a(n-2) for n>=3 [From Jaume Oliver Lafont 
               (joliverlafont(AT)gmail.com), Dec 01 2009]
%Y A001048 Apart from initial terms, same as A059171.
%Y A001048 Contribution from Johannes W. Meijer (meijgia(AT)hotmail.com), Jul 21 
               2009: (Start)
%Y A001048 Equals the square root of the first right hand column of A162990.
%Y A001048 (End)
%Y A001048 Sequence in context: A078918 A054104 A053556 this_sequence A141520 A072042 
               A162074
%Y A001048 Adjacent sequences: A001045 A001046 A001047 this_sequence A001049 A001050 
               A001051
%K A001048 nonn,easy,new
%O A001048 1,1
%A A001048 N. J. A. Sloane (njas(AT)research.att.com), R. K. Guy
%E A001048 More terms from James A. Sellers (sellersj(AT)math.psu.edu), Sep 19 2000

Search completed in 0.002 seconds