1,1

Number of {12,12*,1*2,21,21*}-avoiding signed permutations in the hyperoctahedral group.

a(n)=the hook product of the shape (n,1). - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 13 2004

Archimedeans Problems Drive, Eureka, 24 (1961), 20.

Biondi, E.; Divieti, L.; Guardabassi, G.; Counting paths, circuits, chains, and cycles in graphs: A unified approach. Canad. J. Math. 22 1970 22-35.

T. D. Noe, Table of n, a(n) for n=1..100

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 97

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 641

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 101

Eric Weisstein's World of Mathematics, Uniform Sum Distribution

Index entries for sequences related to factorial numbers

T. Mansour and J. West, Avoiding 2-letter signed patterns.

a(n) = (n+1)(n-1)!.

E.g.f.: x/(1-x) - ln(1-x). - Ralf Stephan, Apr 11 2004

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

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

Apart from initial terms, same as A059171.

Adjacent sequences: A001045 A001046 A001047 this_sequence A001049 A001050 A001051

Sequence in context: A078918 A054104 A053556 this_sequence A141520 A072042 A082569

nonn,easy

njas, R. K. Guy

More terms from James A. Sellers (sellersj(AT)math.psu.edu), Sep 19 2000