a(n) = (4*n^3 + 11*n^2 + 9*n + 2)/2.

Terms

a(0) =1a(1) =13a(2) =48a(3) =118a(4) =235a(5) =411a(6) =658a(7) =988a(8) =1413a(9) =1945a(10) =2596a(11) =3378a(12) =4303a(13) =5383a(14) =6630a(15) =8056a(16) =9673a(17) =11493a(18) =13528a(19) =15790a(20) =18291a(21) =21043a(22) =24058a(23) =27348a(24) =30925a(25) =34801a(26) =38988a(27) =43498a(28) =48343a(29) =53535