Difference triangle of factorial numbers read by upward diagonals.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =6a(6) =11a(7) =14a(8) =18a(9) =24a(10) =53a(11) =64a(12) =78a(13) =96a(14) =120a(15) =309a(16) =362a(17) =426a(18) =504a(19) =600a(20) =720a(21) =2119a(22) =2428a(23) =2790a(24) =3216a(25) =3720a(26) =4320a(27) =5040a(28) =16687a(29) =18806