a(n) = 2*(n+1) + 3*n + ... + (k+1)*(n+2-k), where k = floor(n/2).

Terms

a(0) =6a(1) =8a(2) =22a(3) =27a(4) =52a(5) =61a(6) =100a(7) =114a(8) =170a(9) =190a(10) =266a(11) =293a(12) =392a(13) =427a(14) =552a(15) =596a(16) =750a(17) =804a(18) =990a(19) =1055a(20) =1276a(21) =1353a(22) =1612a(23) =1702a(24) =2002a(25) =2106a(26) =2450a(27) =2569a(28) =2960a(29) =3095