a(n) = 25*n^2/2 - 11*n/2 + 1.

Terms

a(0) =1a(1) =8a(2) =40a(3) =97a(4) =179a(5) =286a(6) =418a(7) =575a(8) =757a(9) =964a(10) =1196a(11) =1453a(12) =1735a(13) =2042a(14) =2374a(15) =2731a(16) =3113a(17) =3520a(18) =3952a(19) =4409a(20) =4891a(21) =5398a(22) =5930a(23) =6487a(24) =7069a(25) =7676a(26) =8308a(27) =8965a(28) =9647a(29) =10354