Hit polynomials.

Terms

a(0) =3a(1) =6a(2) =44a(3) =180a(4) =1407a(5) =10384a(6) =92896a(7) =911512a(8) =9913152a(9) =117788056a(10) =1519021046a(11) =21123287848a(12) =315034832581