a(n) = hypergeom([-1 - n, -n, 1 - n], [2, 3], -3).

A368733

a(n) = hypergeom([-1 - n, -n, 1 - n], [2, 3], -3).

Terms

    a(0) =1a(1) =1a(2) =4a(3) =22a(4) =148a(5) =1132a(6) =9484a(7) =85066a(8) =804556a(9) =7939738a(10) =81128800a(11) =853424464a(12) =9201391456a(13) =101327618056

External references