(-1)^(n+1)/2*sum(k=1,2n,C(2n+1,k)*B(k)*4^k) where C(n,k) are the binomial coefficients, B(k) the Bernoulli numbers.

A069989

(-1)^(n+1)/2*sum(k=1,2n,C(2n+1,k)*B(k)*4^k) where C(n,k) are the binomial coefficients, B(k) the Bernoulli numbers.

Terms

    a(0) =1a(1) =13a(2) =213a(3) =6233a(4) =277865a(5) =17567973a(6) =1495207357a(7) =164827853233

External references