a(n) = 5^(2*n)*(5^(2*n)-1)*Bernoulli(2*n)/(2*n).

A047683

a(n) = 5^(2*n)*(5^(2*n)-1)*Bernoulli(2*n)/(2*n).

Terms

    a(0) =50a(1) =-3250a(2) =968750a(3) =-635781250a(4) =722480468750

External references