G.f.: exp( Sum_{n>=1} A174462(n)*x^n/n ) where A174462(n) = Sum_{d|n} C(n,d)^2.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =21a(5) =32a(6) =174a(7) =236a(8) =1310a(9) =2609a(10) =12579a(11) =18150a(12) =150980a(13) =198821a(14) =1471346a(15) =2645433a(16) =17956158a(17) =24534384a(18) =234506155a(19) =304507520a(20) =2773986000a(21) =4315363549a(22) =36311714888a(23) =47769153478a(24) =500399410005a(25) =637747787407