Main diagonal of the array A059503.

Terms

a(0) =1a(1) =5a(2) =19a(3) =66a(4) =216a(5) =679a(6) =2075a(7) =6211a(8) =18299a(9) =53244a(10) =153366a(11) =438095a(12) =1242709a(13) =3504161a(14) =9830371a(15) =27454614a(16) =76375860a(17) =211732471a(18) =585157679a(19) =1612689439a(20) =4433421131a(21) =12160156560a(22) =33284285874a(23) =90931830431a(24) =247991356201a(25) =675243561149