15-gonal (or pentadecagonal) numbers: n*(13n-11)/2.

Terms

a(0) =0a(1) =1a(2) =15a(3) =42a(4) =82a(5) =135a(6) =201a(7) =280a(8) =372a(9) =477a(10) =595a(11) =726a(12) =870a(13) =1027a(14) =1197a(15) =1380a(16) =1576a(17) =1785a(18) =2007a(19) =2242a(20) =2490a(21) =2751a(22) =3025a(23) =3312a(24) =3612a(25) =3925a(26) =4251a(27) =4590a(28) =4942a(29) =5307