27-gonal numbers: a(n) = n*(25*n-23)/2.

Terms

a(0) =0a(1) =1a(2) =27a(3) =78a(4) =154a(5) =255a(6) =381a(7) =532a(8) =708a(9) =909a(10) =1135a(11) =1386a(12) =1662a(13) =1963a(14) =2289a(15) =2640a(16) =3016a(17) =3417a(18) =3843a(19) =4294a(20) =4770a(21) =5271a(22) =5797a(23) =6348a(24) =6924a(25) =7525a(26) =8151a(27) =8802a(28) =9478a(29) =10179