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%I #17 Dec 22 2014 12:10:31
%S 1,1,10,5,42,14,60,15,110,22,5460,910,420,60,2040,255,11970,1330,
%T 23100,2310,15180,1380,163800,13650,3276,252,8120,580,286440,19096,
%U 314160,19635,3570,210,11515140,639730,103740,5460
%N a(n) = -A141055(n)/(n+1)!.
%C 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).
%F a(2n) / a(2n+1) = n + 1.
%p A141055 := proc(n) if n = 0 then -1; else procname(n-1)*A027760(n+2) ; end if; end proc:
%p A141321 := proc(n) -A141055(n)/(n+1)! ; end proc: # _R. J. Mathar_, Jul 08 2011
%t (* 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 *)
%o (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
%Y Cf. A027760, A141055.
%K nonn,less
%O 0,3
%A _Paul Curtz_, Aug 02 2008