Hit polynomials.

Terms

a(0) =2a(1) =2a(2) =10a(3) =28a(4) =207a(5) =1288a(6) =10366a(7) =91296a(8) =903037a(9) =9832848a(10) =117032570a(11) =1510932116a(12) =21028774738a(13) =313832463386