E.g.f. exp(x+x^3/6).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =11a(6) =31a(7) =106a(8) =337a(9) =1205a(10) =5021a(11) =20186a(12) =86461a(13) =417847a(14) =1992355a(15) =9860306a(16) =53734241a(17) =292816841a(18) =1633818457a(19) =9855157330a(20) =59926837141a(21) =370352343971