A013624 Triangle of coefficients in expansion of (3+7x)^n.

1, 3, 7, 9, 42, 49, 27, 189, 441, 343, 81, 756, 2646, 4116, 2401, 243, 2835, 13230, 30870, 36015, 16807, 729, 10206, 59535, 185220, 324135, 302526, 117649, 2187, 35721, 250047, 972405, 2268945, 3176523, 2470629, 823543, 6561, 122472