a(n) = (1/7) * Sum_{k=0..n-1} binomial(7*n,7*k+1).

A387748

a(n) = (1/7) * Sum_{k=0..n-1} binomial(7*n,7*k+1).

Terms

    a(0) =0a(1) =1a(2) =431a(3) =36825a(4) =5846719a(5) =678491425a(6) =91158006047

External references