Main diagonal of rectangular table A124460.

Terms

a(0) =1a(1) =2a(2) =8a(3) =44a(4) =302a(5) =2437a(6) =22143a(7) =220663a(8) =2377322a(9) =27462836a(10) =338270681a(11) =4422338285a(12) =61114545578a(13) =889542935517