OFFSET
0,2
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
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jul 09 2018, following a suggestion from Doron Zeilberger
STATUS
approved