Hit polynomials.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =21a(5) =122a(6) =849a(7) =6719a(8) =59873a(9) =593686a(10) =6483027a(11) =77309508a(12) =999569969a(13) =13927664613a(14) =208044077633