First diagonal of A027516.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =15a(5) =70a(6) =154a(7) =105a(8) =77a(9) =55a(10) =165a(11) =120a(12) =4620a(13) =62216a(14) =95445a(15) =72720a(16) =28280a(17) =43632a(18) =239976a(19) =3563280a(20) =2820930a(21) =372362760a(22) =37310748552a(23) =7078607624