G.f. is the polynomial (Product_{k=1..22} (1 - x^(3*k)))/(1-x)^22.

Terms

a(0) =1a(1) =22a(2) =253a(3) =2023a(4) =12628a(5) =65527a(6) =293985a(7) =1171368a(8) =4226112a(9) =14009116a(10) =43155475a(11) =124666555a(12) =340214160a(13) =882447555a(14) =2186642775a(15) =5198778091a(16) =11903438767a(17) =26332159753a(18) =56436426134a(19) =117478662620a(20) =238027900220a(21) =470331123901