OFFSET
0,2
COMMENTS
Two involutions x,y commute if x*y = y*x. Isomorphism is up to permutation of the elements of the (2n)-set. a(n) also gives the value for a (2n+1)-set.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (8, -21, 0, 106, -176, -70, 512, -435, -392, 1001, -512, -580, 1120, -580, -512, 1001, -392, -435, 512, -70, -176, 106, 0, -21, 8, -1).
FORMULA
G.f.: 1/((1 - x)^16*(1 + x)^8*(1 + x^2)).
PROG
(PARI) C(3, 30) \\ C(k, n) defined in A362903.
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, May 11 2023
STATUS
approved