A070734 Order of the subgroup of the symmetric group S_n generated by the cycles (1,2,3) and (1,2,3,...,n).

3, 24, 60, 720, 2520, 40320, 181440, 3628800, 19958400, 479001600, 3113510400, 87178291200, 653837184000, 20922789888000, 177843714048000, 6402373705728000, 60822550204416000, 2432902008176640000

Offset

3,1

Links

Table of n, a(n) for n=3..20.

Formula

For odd n: a(n) = n!/2; for even n: a(n) = n!.

a(n) = (1/4)*(3+(-1)^n)*n! - Benoit Cloitre, May 18 2002

From Amiram Eldar, Jul 06 2022: (Start)

Sum_{n>=3} 1/a(n) = 2*sinh(1) + cosh(1) - 7/2.

Sum_{n>=3} (-1)^(n+1)/a(n) = 2*sinh(1) - cosh(1) - 1/2. (End)

Mathematica

f[n_] := If[ EvenQ[n], n!, n!/2]; Table[ f[n], {n, 3, 24}].

Prog

(PARI) for(n=3, 20, print1((3+(-1)^n)/4*n!, ", "))

Crossrefs

Cf. A000142, A001710.

Sequence in context: A220868 A296273 A101008 * A009113 A152751 A369953

Adjacent sequences: A070731 A070732 A070733 * A070735 A070736 A070737

Keyword

nonn,easy

Author

Sharon Sela (sharonsela(AT)hotmail.com), May 14 2002

Extensions

More terms from Benoit Cloitre, May 18 2002

Status

approved