a(n) = (2*n^3 + 5*n^2 + 11*n)/2.

Terms

a(0) =9a(1) =29a(2) =66a(3) =126a(4) =215a(5) =339a(6) =504a(7) =716a(8) =981a(9) =1305a(10) =1694a(11) =2154a(12) =2691a(13) =3311a(14) =4020a(15) =4824a(16) =5729a(17) =6741a(18) =7866a(19) =9110a(20) =10479a(21) =11979a(22) =13616a(23) =15396a(24) =17325a(25) =19409a(26) =21654a(27) =24066a(28) =26651a(29) =29415