Heptagonal numbers (or 7-gonal numbers): n*(5*n-3)/2.

Terms

a(0) =0a(1) =1a(2) =7a(3) =18a(4) =34a(5) =55a(6) =81a(7) =112a(8) =148a(9) =189a(10) =235a(11) =286a(12) =342a(13) =403a(14) =469a(15) =540a(16) =616a(17) =697a(18) =783a(19) =874a(20) =970a(21) =1071a(22) =1177a(23) =1288a(24) =1404a(25) =1525a(26) =1651a(27) =1782a(28) =1918a(29) =2059