14541120domain: NAppears in sequencesa(1) = 1, a(2) = 2; for n>2, a(n) = sum_{r=1..n} {sum of all previous terms taken r at a time}.at n=7A089709Determinant of n X n matrix whose main diagonal consists of the first n 7-gonal numbers and all other elements are 1's.at n=5A302911