A069660 Order of the subgroup of the symmetric group S_n generated by the cycles (1,3) and (1,2,3,...,n).

6, 8, 120, 72, 5040, 1152, 362880, 28800, 39916800, 1036800, 6227020800, 50803200, 1307674368000, 3251404800, 355687428096000, 263363788800, 121645100408832000, 26336378880000, 51090942171709440000

Offset

3,1

Links

Table of n, a(n) for n=3..21.

Formula

If n is odd a(n) = n!, if n is even a(n) = 2 * ((n/2)!)^2 = 2 * n! / A000984(n/2) = 2 * A001044(n/2).

Crossrefs

Cf. A000984, A070734, A000142, A009445, A001044.

Sequence in context: A161801 A211041 A236754 * A119001 A324987 A013239

Adjacent sequences: A069657 A069658 A069659 * A069661 A069662 A069663

Keyword

nonn,easy

Author

Sharon Sela (sharonsela(AT)hotmail.com), May 16 2002

Extensions

More terms from Benoit Cloitre, May 20 2002

Status

approved