a(n) = n*(4*n^2 - 3*n + 5)/6.

Terms

a(0) =1a(1) =5a(2) =16a(3) =38a(4) =75a(5) =131a(6) =210a(7) =316a(8) =453a(9) =625a(10) =836a(11) =1090a(12) =1391a(13) =1743a(14) =2150a(15) =2616a(16) =3145a(17) =3741a(18) =4408a(19) =5150a(20) =5971a(21) =6875a(22) =7866a(23) =8948a(24) =10125a(25) =11401a(26) =12780a(27) =14266a(28) =15863a(29) =17575