A086985 a(n) = A000407(n) - A086984(n).

0, 0, 0, 144, 6000, 198000, 6420960, 218453760, 7988440320, 316674489600, 13630070361600, 635880851020800, 32050874586931200, 1738651147833600000, 101100246720625152000, 6277170099060596736000, 414620927349422137344000

Offset

1,4

Links

Table of n, a(n) for n=1..17.

Formula

a(n) = (2*n-1)!/(n-1)! - n! - Sum_{i=2..n} binomial(n-1, n-i)*n*n!.

a(n) = (2*n-1)!/(n-1)! - n! - (2^(n-1) - 1)*n*n!. - Stefano Spezia, Mar 07 2025

Mathematica

a[n_]:=(2*n-1)!/(n-1)!-n!-(2^(n-1)-1)*n*n!; Array[a, 17] (* Stefano Spezia, Mar 07 2025 *)

Prog

(PARI) a(n)=(2*n-1)!/(n-1)!-n!-sum(i=2, n, binomial(n-1, n-i)*n*n!)

Crossrefs

Cf. A000407, A086984.

Sequence in context: A262788 A319294 A233645 * A371251 A259318 A231744

Adjacent sequences: A086982 A086983 A086984 * A086986 A086987 A086988

Keyword

nonn,changed

Author

Jon Perry, Jul 27 2003

Status

approved