9-gonal (or enneagonal or nonagonal) numbers: a(n) = n*(7*n-5)/2.

Terms

a(0) =0a(1) =1a(2) =9a(3) =24a(4) =46a(5) =75a(6) =111a(7) =154a(8) =204a(9) =261a(10) =325a(11) =396a(12) =474a(13) =559a(14) =651a(15) =750a(16) =856a(17) =969a(18) =1089a(19) =1216a(20) =1350a(21) =1491a(22) =1639a(23) =1794a(24) =1956a(25) =2125a(26) =2301a(27) =2484a(28) =2674a(29) =2871