a(n) = 26*n^2.

Terms

a(0) =0a(1) =26a(2) =104a(3) =234a(4) =416a(5) =650a(6) =936a(7) =1274a(8) =1664a(9) =2106a(10) =2600a(11) =3146a(12) =3744a(13) =4394a(14) =5096a(15) =5850a(16) =6656a(17) =7514a(18) =8424a(19) =9386a(20) =10400a(21) =11466a(22) =12584a(23) =13754a(24) =14976a(25) =16250a(26) =17576a(27) =18954a(28) =20384a(29) =21866