Expansion of 1/(1-x*c(x)^3), c(x) the g.f. of A000108.

Terms

a(0) =1a(1) =1a(2) =4a(3) =16a(4) =65a(5) =267a(6) =1105a(7) =4597a(8) =19196a(9) =80380a(10) =337284a(11) =1417582a(12) =5965622a(13) =25130844a(14) =105954110a(15) =447015744a(16) =1886996681a(17) =7969339643a(18) =33670068133a(19) =142301618265a(20) =601586916703