First differences of A036449, triangular numbers by definition.

Terms

a(0) =1a(1) =3a(2) =21a(3) =171a(4) =1485a(5) =435a(6) =16653a(7) =149331a(8) =1342341a(9) =12076155a(10) =990528a(11) =1279200a(12) =263901a(13) =169071a(14) =446985a(15) =133865703a(16) =1180416a(17) =1214185281a(18) =2366400a(19) =25045503a(20) =247275441a(21) =8923200a(22) =19634511a(23) =56525028a(24) =229847520a(25) =739374285a(26) =224497455a(27) =81939201a(28) =24010841091a(29) =1106357280