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A261428 Number of permutations p of [2n] without fixed points such that p^8 = Id. 3
1, 1, 9, 105, 7665, 303345, 25893945, 1765268505, 345763843425, 42813526781025, 9399638261838825, 1573582072888650825, 563295733721953657425, 139523356060051359020625, 55722660999371761475705625, 17053184982967015188566885625, 9496879931794641573011009810625 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..250

FORMULA

a(n) = (2n)! * [x^(2n)] exp(x^2/2+x^4/4+x^8/8).

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=[2, 4, 8])))

    end:

a:= n-> b(2*n):

seq(a(n), n=0..20);

CROSSREFS

Bisection of column k=8 of A261430.

Cf. A053498.

Sequence in context: A110698 A012485 A052503 * A122569 A316145 A039619

Adjacent sequences:  A261425 A261426 A261427 * A261429 A261430 A261431

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Aug 18 2015

STATUS

approved

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Last modified July 19 04:25 EDT 2019. Contains 325144 sequences. (Running on oeis4.)