Diagonal of triangular array in A079520.

Terms

a(0) =0a(1) =1a(2) =3a(3) =10a(4) =31a(5) =105a(6) =343a(7) =1198a(8) =4056a(9) =14506a(10) =50350a(11) =183284a(12) =647809a(13) =2390121a(14) =8564543a(15) =31933830a(16) =115664164a(17) =434920398a(18) =1588917802a(19) =6016012236a(20) =22134533070a(21) =84289034154a(22) =311957090678