a(n) = n*(14*n - 1).

Terms

a(0) =0a(1) =13a(2) =54a(3) =123a(4) =220a(5) =345a(6) =498a(7) =679a(8) =888a(9) =1125a(10) =1390a(11) =1683a(12) =2004a(13) =2353a(14) =2730a(15) =3135a(16) =3568a(17) =4029a(18) =4518a(19) =5035a(20) =5580a(21) =6153a(22) =6754a(23) =7383a(24) =8040a(25) =8725a(26) =9438a(27) =10179a(28) =10948a(29) =11745