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 A261431 Number of permutations p of [n] without fixed points such that p^n = Id. 3
 1, 0, 1, 2, 9, 24, 175, 720, 7665, 42560, 436401, 3628800, 70215145, 479001600, 7116730335, 88966701824, 1653438211425, 20922789888000, 457688776369825, 6402373705728000, 145083396337080201, 2457732174030848000, 55735573291977790575, 1124000727777607680000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..450 FORMULA a(n) = n! * [x^n] exp(Sum_{d|n, d>1} x^d/d). MAPLE with(numtheory): A:= proc(n, k) option remember; `if`(n<0, 0, `if`(n=0, 1,       add(mul(n-i, i=1..j-1)*A(n-j, k), j=divisors(k) minus {1})))     end: a:= n-> A(n\$2): seq(a(n), n=0..25); MATHEMATICA A[n_, k_] := A[n, k] = If[n < 0, 0, If[n == 0, 1, Sum[Product[n - i, {i, 1, j - 1}] A[n - j, k], {j, Divisors[k] ~Complement~ {1}}]]]; a[n_] := A[n, n]; Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Mar 23 2017, translated from Maple *) CROSSREFS Main diagonal of A261430. Cf. A074759. Sequence in context: A006973 A137852 A097346 * A226388 A053194 A005582 Adjacent sequences:  A261428 A261429 A261430 * A261432 A261433 A261434 KEYWORD nonn AUTHOR Alois P. Heinz, Aug 18 2015 STATUS approved

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Last modified August 13 19:30 EDT 2020. Contains 336451 sequences. (Running on oeis4.)