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

A387817

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

Terms

    a(0) =3a(1) =55a(2) =24463a(3) =2043275a(4) =328589491a(5) =37923176863

External references