a(n) = (n-1)*binomial(3*n-2,n)/(2*n-1) + (n+1)*binomial(3*n,n)/(2*n+1) - binomial(3*n-1,n).

A262717

a(n) = (n-1)*binomial(3*n-2,n)/(2*n-1) + (n+1)*binomial(3*n,n)/(2*n+1) - binomial(3*n-1,n).

Terms

    a(0) =1a(1) =0a(2) =1a(3) =6a(4) =35a(5) =208a(6) =1260a(7) =7752a(8) =48279a(9) =303600a(10) =1924065a(11) =12271350a(12) =78676884a(13) =506662016a(14) =3275052040a(15) =21238169904a(16) =138111313215a(17) =900331830048

External references