E.g.f.: -log( Sum_{n>=0} (-x)^(n^2) / (n^2)! ).

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =19a(5) =90a(6) =510a(7) =3395a(8) =25831a(9) =221140a(10) =2104310a(11) =22027170a(12) =251540795a(13) =3111928820a(14) =41460769350a(15) =591847005749