a(n) = (2*n^3 + 5*n^2 + 7*n)/2.

Terms

a(0) =7a(1) =25a(2) =60a(3) =118a(4) =205a(5) =327a(6) =490a(7) =700a(8) =963a(9) =1285a(10) =1672a(11) =2130a(12) =2665a(13) =3283a(14) =3990a(15) =4792a(16) =5695a(17) =6705a(18) =7828a(19) =9070a(20) =10437a(21) =11935a(22) =13570a(23) =15348a(24) =17275a(25) =19357a(26) =21600a(27) =24010a(28) =26593a(29) =29355