a(n) = ( 2*n*(2*n^2 + 11*n + 26) - (-1)^n + 1 )/16.

Terms

a(0) =0a(1) =5a(2) =14a(3) =29a(4) =51a(5) =82a(6) =123a(7) =176a(8) =242a(9) =323a(10) =420a(11) =535a(12) =669a(13) =824a(14) =1001a(15) =1202a(16) =1428a(17) =1681a(18) =1962a(19) =2273a(20) =2615a(21) =2990a(22) =3399a(23) =3844a(24) =4326a(25) =4847a(26) =5408a(27) =6011a(28) =6657a(29) =7348