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A261429
Number of permutations p of [3n] without fixed points such that p^9 = Id.
3
1, 2, 40, 42560, 17987200, 8116908800, 43924225945600, 108050180446208000, 215140299047145472000, 2906668948375666073600000, 21059302309493030917734400000, 112131367456110324265700556800000, 2891761281909068919518711775232000000
OFFSET
0,2
LINKS
FORMULA
a(n) = (3n)! * [x^(3n)] exp(x^3/3+x^9/9).
MAPLE
b:= proc(n) option remember; `if`(n<0, 0, `if`(n=0, 1,
add(mul(n-i, i=1..j-1)*b(n-j), j=[3, 9])))
end:
a:= n-> b(3*n):
seq(a(n), n=0..15);
CROSSREFS
Trisection of column k=9 of A261430.
Cf. A053499.
Sequence in context: A059476 A306839 A297385 * A062769 A033841 A107194
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 18 2015
STATUS
approved