A316331 a(n) = A000085(4*n+1)/2^n.

1, 13, 655, 71063, 13237457, 3748521653, 1495006933759, 796798642614895, 546144645571635169, 467512355698028529821, 488384275088035513080239, 611057820865315450415912327, 901643505614430586911510015025, 1548711768835068239482321088560837

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, A316332, A316333.