a(n) = (8*n^3 + 12*n^2 + 4*n - 9)/3.

Terms

a(0) =5a(1) =37a(2) =109a(3) =237a(4) =437a(5) =725a(6) =1117a(7) =1629a(8) =2277a(9) =3077a(10) =4045a(11) =5197a(12) =6549a(13) =8117a(14) =9917a(15) =11965a(16) =14277a(17) =16869a(18) =19757a(19) =22957a(20) =26485a(21) =30357a(22) =34589a(23) =39197a(24) =44197a(25) =49605a(26) =55437a(27) =61709a(28) =68437a(29) =75637