a(n) = (1/(2*n+1)) * Sum_{k=0..n} k^3 * (2*k+1) * binomial(3*n-k,n-k).

A390972

a(n) = (1/(2*n+1)) * Sum_{k=0..n} k^3 * (2*k+1) * binomial(3*n-k,n-k).

Terms

    a(0) =0a(1) =1a(2) =11a(3) =79a(4) =508a(5) =3148a(6) =19266a(7) =117579a(8) =718520a(9) =4404465a(10) =27102153a(11) =167440548a(12) =1038594736a(13) =6466829512a(14) =40411517734a(15) =253389362883

External references