A141321 a(n) = -A141055(n)/(n+1)!.

1, 1, 10, 5, 42, 14, 60, 15, 110, 22, 5460, 910, 420, 60, 2040, 255, 11970, 1330, 23100, 2310, 15180, 1380, 163800, 13650, 3276, 252, 8120, 580, 286440, 19096, 314160, 19635, 3570, 210, 11515140, 639730, 103740, 5460

Offset: 0

Author

Paul Curtz, Aug 02 2008

Keywords

• nonn
• less

Comments

a(n+1)/a(n)= 2/2, 30/3, 2/4, 42/5, 2/6, 30/7, 2/8, 66/9, 2/10, 2730/11, 2/12 = A027760(n+2)/(n+1), see A141410. Numerators are also A141056(n+3).

Crossrefs

Cf. A027760, A141055.

Programs

Maple

A141055 := proc(n) if n = 0 then -1; else procname(n-1)*A027760(n+2) ; end if; end proc:
A141321 := proc(n) -A141055(n)/(n+1)! ; end proc: # R. J. Mathar, Jul 08 2011

Mathematica

(* b = A141055 *) b[n_] := b[n] = b[n-1]*If[OddQ[n], 2, Denominator[BernoulliB[n+2]]]; b[0]=-1; a[n_] := -b[n]/(n+1)!; Table[a[n], {n, 0, 37}] (* Jean-François Alcover, Dec 18 2014 *)

PARI

a(n)=if(n, my(pr=a(n-1)); fordiv(n+2, d, if(isprime(d+1), pr*=d+1)); pr, 1)/(n+1) \\ Charles R Greathouse IV, Jul 08 2011

Formula

a(2n) / a(2n+1) = n + 1.