6 times pentagonal numbers: a(n) = 3*n*(3*n-1).

Terms

a(0) =0a(1) =6a(2) =30a(3) =72a(4) =132a(5) =210a(6) =306a(7) =420a(8) =552a(9) =702a(10) =870a(11) =1056a(12) =1260a(13) =1482a(14) =1722a(15) =1980a(16) =2256a(17) =2550a(18) =2862a(19) =3192a(20) =3540a(21) =3906a(22) =4290a(23) =4692a(24) =5112a(25) =5550a(26) =6006a(27) =6480a(28) =6972a(29) =7482