Bell triangle A011971 squared.

Terms

a(0) =1a(1) =3a(2) =4a(3) =15a(4) =21a(5) =25a(6) =107a(7) =149a(8) =200a(9) =225a(10) =1054a(11) =1420a(12) =1909a(13) =2479a(14) =2704a(15) =13684a(16) =17814a(17) =23313a(18) =30439a(19) =38505a(20) =41209a(21) =224071a(22) =283592a(23) =360853a(24) =461015a(25) =587641a(26) =727920a(27) =769129a(28) =4471699a(29) =5535812