a(n) = 25*n^2 + 25*n + 6.

Terms

a(0) =6a(1) =56a(2) =156a(3) =306a(4) =506a(5) =756a(6) =1056a(7) =1406a(8) =1806a(9) =2256a(10) =2756a(11) =3306a(12) =3906a(13) =4556a(14) =5256a(15) =6006a(16) =6806a(17) =7656a(18) =8556a(19) =9506a(20) =10506a(21) =11556a(22) =12656a(23) =13806a(24) =15006a(25) =16256a(26) =17556a(27) =18906a(28) =20306a(29) =21756