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A239778 Number of pairs of functions f, g from a size n set into itself satisfying f(f(f(x))) = f(g(g(x))). 0
1, 1, 12, 255, 8968, 452485, 31456656, 2899786855 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
MAPLE
s:= proc(n, i) option remember; `if`(i=0, [[]],
map(x-> seq([j, x[]], j=1..n), s(n, i-1)))
end:
a:= proc(n) (l-> add(add(`if`([true$n]=[seq(evalb(
f[f[f[i]]]=f[g[g[i]]]), i=1..n)], 1, 0), g=l), f=l))(s(n$2))
end:
seq(a(n), n=0..5); # Alois P. Heinz, Jul 16 2014
CROSSREFS
Sequence in context: A129585 A034672 A133285 * A113091 A053324 A297717
KEYWORD
nonn,more
AUTHOR
Chad Brewbaker, Mar 26 2014
EXTENSIONS
a(6)-a(7) from Giovanni Resta, Mar 28 2014
STATUS
approved

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Last modified March 28 17:25 EDT 2024. Contains 371254 sequences. (Running on oeis4.)