a(n) = n*(n+1)^2/2.

Terms

a(0) =0a(1) =2a(2) =9a(3) =24a(4) =50a(5) =90a(6) =147a(7) =224a(8) =324a(9) =450a(10) =605a(11) =792a(12) =1014a(13) =1274a(14) =1575a(15) =1920a(16) =2312a(17) =2754a(18) =3249a(19) =3800a(20) =4410a(21) =5082a(22) =5819a(23) =6624a(24) =7500a(25) =8450a(26) =9477a(27) =10584a(28) =11774a(29) =13050