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A316333
a(n) = A000085(4*n+3)/2^(n+2).
4
1, 29, 2231, 323423, 75151585, 25451905333, 11799518538967, 7161375112402823, 5503252915369107329, 5217568316626716585485, 5977663757214838174587319, 8136442760259565566724537711, 12972630954295515566319694027489, 23938932303527622015634131021262757
OFFSET
0,2
LINKS
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