28-gonal pyramidal numbers: a(n) = n*(n+1)*(26*n-23)/6.

Terms

a(0) =0a(1) =1a(2) =29a(3) =110a(4) =270a(5) =535a(6) =931a(7) =1484a(8) =2220a(9) =3165a(10) =4345a(11) =5786a(12) =7514a(13) =9555a(14) =11935a(15) =14680a(16) =17816a(17) =21369a(18) =25365a(19) =29830a(20) =34790a(21) =40271a(22) =46299a(23) =52900a(24) =60100a(25) =67925a(26) =76401a(27) =85554a(28) =95410a(29) =105995