a(n) = (1/7) * Sum_{k=0..n-1} binomial(7*n,7*k+3).

A387750

a(n) = (1/7) * Sum_{k=0..n-1} binomial(7*n,7*k+3).

Terms

    a(0) =0a(1) =5a(2) =195a(3) =51433a(4) =4945863a(5) =734061693a(6) =87730167995

External references