a(n) = (2*n^3 + 5*n^2 + 21*n)/2.

Terms

a(0) =14a(1) =39a(2) =81a(3) =146a(4) =240a(5) =369a(6) =539a(7) =756a(8) =1026a(9) =1355a(10) =1749a(11) =2214a(12) =2756a(13) =3381a(14) =4095a(15) =4904a(16) =5814a(17) =6831a(18) =7961a(19) =9210a(20) =10584a(21) =12089a(22) =13731a(23) =15516a(24) =17450a(25) =19539a(26) =21789a(27) =24206a(28) =26796a(29) =29565