A130637 a(n) = n*a(n-2) + a(n-5) for n >= 5 and with a(0)=0, a(1)=1, a(2)=0, a(3)=3, a(4)=0.

0, 1, 0, 3, 0, 15, 1, 105, 11, 945, 125, 10396, 1605, 135159, 23415, 2027510, 385036, 34469275, 7065807, 654939640, 143343650, 13754117476, 3188029575, 316351767755, 77167649440, 7908937537525, 2020113002916, 213544501542750, 56879515849403, 6192867712389190

Offset

0,4

Links

Table of n, a(n) for n=0..29.

Formula

a(n) = n*a(n-2) + a(n-5) for n >= 5. - Jianing Song, Oct 10 2018

Mathematica

RecurrenceTable[{a[0] == 0, a[1] == 1, a[2] == 0, a[3] == 3, a[4] == 0, a[n] == n a[n - 2] + a[n - 5]}, a, {n, 0, 30}] (* Bruno Berselli, Oct 11 2018 *)

Prog

(PARI) a(n) = if(n<5, (n==1) + 3*(n==3), n*a(n-2) + a(n-5)) \\ Jianing Song, Oct 10 2018
(Magma) I:=[0, 1, 0, 3, 0]; [n le 5 select I[n]  else (n-1)*Self(n-2)+Self(n-5): n in [1..30]]; // Vincenzo Librandi, Oct 11 2018

Crossrefs

Sequence in context: A277936 A138540 A123023 * A365419 A366410 A054882

Adjacent sequences: A130634 A130635 A130636 * A130638 A130639 A130640

Keyword

nonn,easy

Author

Roger L. Bagula, Jun 19 2007

Extensions

Edited, new name, and offset corrected by Jianing Song, Oct 10 2018

Status

approved