a(n) = 25*n^2 - 2*n.

Terms

a(0) =23a(1) =96a(2) =219a(3) =392a(4) =615a(5) =888a(6) =1211a(7) =1584a(8) =2007a(9) =2480a(10) =3003a(11) =3576a(12) =4199a(13) =4872a(14) =5595a(15) =6368a(16) =7191a(17) =8064a(18) =8987a(19) =9960a(20) =10983a(21) =12056a(22) =13179a(23) =14352a(24) =15575a(25) =16848a(26) =18171a(27) =19544a(28) =20967a(29) =22440