a(1) = 0; for n > 1: a(n) = 2*(prime(n)-1)!/(prime(n)+1).

A130775

a(1) = 0; for n > 1: a(n) = 2*(prime(n)-1)!/(prime(n)+1).

Terms

    a(0) =0a(1) =1a(2) =8a(3) =180a(4) =604800a(5) =68428800

External references