p-INVERT of the positive integers, where p(S) = 1 - S - S^2 - S^3.

Terms

a(0) =1a(1) =4a(2) =15a(3) =55a(4) =198a(5) =706a(6) =2510a(7) =8923a(8) =31737a(9) =112918a(10) =401799a(11) =1429744a(12) =5087461a(13) =18102522a(14) =64413263a(15) =229198253a(16) =815544198a(17) =2901909494a(18) =10325718678a(19) =36741486569a(20) =130735386073a(21) =465189151460