A122017 a(n) = if n even then a(n - 1) - (n - 1)*a(n - 2) otherwise 2*(a(n - 1) + (n - 1)*a(n - 2)).

1, 2, 1, 10, 7, 94, 59, 1246, 833, 21602, 14105, 460250, 305095, 11656190, 7689955, 341753230, 226403905, 11388911170, 7540044785, 425080891690, 281820040775, 17566875749150, 11648654892875, 796239842748350, 528320780212225

Offset

0,2

Links

Table of n, a(n) for n=0..24.

Mathematica

a[0] = 1; a[1] = 2; a[n_] := a[n] = If[Mod[n, 2] == 0, a[n - 1] - (n - 1)*a[n - 2], 2*(a[n - 1] + (n - 1)*a[n - 2])] b = Table[a[n], {n, 0, 30}]
nxt[{n_, a_, b_}]:={n+1, b, If[OddQ[n], b-n*a, 2(b+n*a)]}; NestList[nxt, {1, 1, 2}, 30][[All, 2]] (* Harvey P. Dale, Jun 12 2020 *)

Crossrefs

Cf. A000898, A121966.

Sequence in context: A225470 A081099 A213252 * A219900 A136233 A113088

Adjacent sequences: A122014 A122015 A122016 * A122018 A122019 A122020

Keyword

nonn,easy

Author

Roger L. Bagula, Sep 11 2006

Extensions

Edited by N. J. A. Sloane, Sep 13 2006

Offset corrected by Jason Yuen, Sep 15 2024

Status

approved