28-gonal numbers: a(n) = n*(13*n - 12).

Terms

a(0) =0a(1) =1a(2) =28a(3) =81a(4) =160a(5) =265a(6) =396a(7) =553a(8) =736a(9) =945a(10) =1180a(11) =1441a(12) =1728a(13) =2041a(14) =2380a(15) =2745a(16) =3136a(17) =3553a(18) =3996a(19) =4465a(20) =4960a(21) =5481a(22) =6028a(23) =6601a(24) =7200a(25) =7825a(26) =8476a(27) =9153a(28) =9856a(29) =10585