a(n) = binomial(5*n,n)*(3*n+1)/(4*n+1).

A215541

a(n) = binomial(5*n,n)*(3*n+1)/(4*n+1).

Terms

    a(0) =1a(1) =4a(2) =35a(3) =350a(4) =3705a(5) =40480a(6) =451269a(7) =5101360a(8) =58261125a(9) =670609940a(10) =7766844470a(11) =90404916420

External references