A316332 a(n) = A000085(4*n+2)/2^(n+1).

1, 19, 1187, 149405, 31166057, 9670072483, 4163946939067, 2370770585582221, 1722046856020416785, 1552401874990891104371, 1699257737580930574489619, 2218555640616875773883091901, 3404174268230266459851637679353, 6062646848508401565245592651382915, 12398960005973049406349011215379703723

Offset: 0

Author

N. J. A. Sloane, Jul 09 2018, following a suggestion from Doron Zeilberger

Keywords

• nonn

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..210
• S. Chowla, I. N. Herstein and W. K. Moore, On recursions connected with symmetric groups I, Canad. J. Math. 3 (1951) 328-334.
• Dongsu Kim and Jang Soo Kim, A combinatorial approach to the power of 2 in the number of involutions, J. Comb. Theory Ser. A 117 (8) (2010): 1082-1094.

Crossrefs

Cf. A000085, A316330, A316331, A316333.