A217239 a(n) = n!*(!n - 1) = n! * Sum_{k=1..n-1} k!.

0, 0, 2, 18, 216, 3960, 110160, 4399920, 238412160, 16777031040, 1484589254400, 161180565638400, 21054377854540800, 3256459838542310400, 588451470350449305600, 122827588903536701184000, 29325437466043778002944000

Offset

0,3

Comments

Variant of A143217.

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Formula

a(n) = A000142(n) * A007489(n).

a(n) = n!*(!n - 1) = n! * Sum_{k=1..n-1} k!.

Mathematica

Table[n!*Sum[i!, {i, n-1}], {n, 0, 16}]

Prog

(Magma) [0, 0] cat [Factorial(n)*(&+[Factorial(k): k in [1..n-1]]): n in [2..30]]; // G. C. Greubel, Jul 12 2022
(SageMath) f=factorial; [f(n)*sum(f(k) for k in (1..n-1)) for n in (0..40)] # G. C. Greubel, Jul 12 2022

Crossrefs

Cf. A000142, A007489, A061640, A217238.

Sequence in context: A369027 A153647 A052726 * A279045 A155666 A355723

Adjacent sequences: A217236 A217237 A217238 * A217240 A217241 A217242

Keyword

nonn,easy

Author

Olivier Gérard, Sep 28 2012

Status

approved