A073109 a(n) = (Product_{p<=n, p odd prime} p) * Sum_{k=1..n} B(k)*C(2k,k) where B(k) is the k-th Bernoulli number.

0, 0, -7, -35, 295, 2065, -42980, -42980, 1426670, 15693370, -774856236, -10073131068, 692669409432, 692669409432, -63315621131763, -1076365559239971, 126262920264259779, 2398995485020935801, -351338708777824396629, -351338708777824396629

Offset

2,3

Comments

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, ...

Links

Table of n, a(n) for n=2..21.

Prog

(PARI) a(n)=(1/2)*prod(i=1, n, i^isprime(i))*sum(k=1, n, bernfrac(k)*binomial(2*k, k))

Crossrefs

Sequence in context: A096686 A165505 A165639 * A231511 A078235 A364454

Adjacent sequences: A073106 A073107 A073108 * A073110 A073111 A073112

Keyword

easy,sign

Author

Benoit Cloitre, Aug 19 2002

Status

approved