Riordan array (1, x*c(x)*c(-x*c(x))), c(x) the g.f. of A000108.

Terms

a(0) =1a(1) =0a(2) =1a(3) =0a(4) =0a(5) =1a(6) =0a(7) =2a(8) =0a(9) =1a(10) =0a(11) =1a(12) =4a(13) =0a(14) =1a(15) =0a(16) =12a(17) =2a(18) =6a(19) =0a(20) =1a(21) =0a(22) =14a(23) =28a(24) =3a(25) =8a(26) =0a(27) =1a(28) =0a(29) =100