a(n) = A356500(3*n, n+1) for n >= 0.

A356506

a(n) = A356500(3*n, n+1) for n >= 0.

Terms

    a(0) =1a(1) =6a(2) =120a(3) =3250a(4) =103020a(5) =3587696a(6) =133101836a(7) =5167564380a(8) =207615129579

External references