E.g.f. exp(x+x^4).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =25a(5) =121a(6) =361a(7) =841a(8) =21841a(9) =184465a(10) =912241a(11) =3334321a(12) =89824681a(13) =1063799881a(14) =7325422105a(15) =36454050361