a(n) = n*(2*n - 3 - (-1)^n)*(5*n - 2 + (-1)^n)/16.

Terms

a(0) =0a(1) =0a(2) =9a(3) =19a(4) =55a(5) =87a(6) =168a(7) =234a(8) =378a(9) =490a(10) =715a(11) =885a(12) =1209a(13) =1449a(14) =1890a(15) =2212a(16) =2788a(17) =3204a(18) =3933a(19) =4455a(20) =5355a(21) =5995a(22) =7084a(23) =7854a(24) =9150a(25) =10062a(26) =11583a(27) =12649a(28) =14413a(29) =15645