a(n) = b(n)*(b(n)+1) = b(n) + ... + c(n), where b(n) = A011916(n), c(n) = A011918(n).

A011920

a(n) = b(n)*(b(n)+1) = b(n) + ... + c(n), where b(n) = A011916(n), c(n) = A011918(n).

Terms

    a(0) =12a(1) =1980a(2) =378840a(3) =73419192a(4) =14241916260

External references