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%I #10 Nov 01 2015 07:55:31
%S 0,0,-7,-35,295,2065,-42980,-42980,1426670,15693370,-774856236,
%T -10073131068,692669409432,692669409432,-63315621131763,
%U -1076365559239971,126262920264259779,2398995485020935801,-351338708777824396629,-351338708777824396629
%N a(n) = Product_{p<=n, p} * Sum_{k=1..n} B(k)*C(2k,k) where B(k) is the k-th Bernoulli number and p denotes the odd primes.
%C a(n) = a(n+1) for n=2, 8, 14, 20, 24, 26, 32, 34, 38, 44, 48, 50, 54, 56, 62, 64, 68, 74, 76, 80, 84, 86, 90, 92, 94, 98...it seems this is true for n=6k+2, n=10k+24, ...
%o (PARI) a(n)=(1/2)*prod(i=1,n,i^isprime(i))*sum(k=1,n,bernfrac(k)*binomial(2*k,k))
%K easy,sign
%O 2,3
%A _Benoit Cloitre_, Aug 19 2002
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