Main diagonal of array A255551.

Terms

a(0) =2a(1) =5a(2) =39a(3) =91a(4) =199a(5) =315a(6) =567a(7) =829a(8) =1227a(9) =1513a(10) =1953a(11) =2569a(12) =3277a(13) =3769a(14) =5119a(15) =5925a(16) =6607a(17) =7539a(18) =8319a(19) =9375a(20) =11007a(21) =12511a(22) =14103a(23) =15801a(24) =17593a(25) =19165a(26) =22213a(27) =23617a(28) =25467a(29) =26967