E.g.f. -log(sech(x) - log(x+1)).

Terms

a(0) =0a(1) =1a(2) =1a(3) =4a(4) =3a(5) =33a(6) =155a(7) =1195a(8) =5418a(9) =72373a(10) =496027a(11) =6851051a(12) =59706592a(13) =986009607a(14) =10430165629a(15) =193892831665