a(n) = (1/24)*(sigma_3(2*n-1) - sigma_1(2*n-1)).

Terms

a(0) =0a(1) =1a(2) =5a(3) =14a(4) =31a(5) =55a(6) =91a(7) =146a(8) =204a(9) =285a(10) =400a(11) =506a(12) =655a(13) =850a(14) =1015a(15) =1240a(16) =1552a(17) =1804a(18) =2109a(19) =2562a(20) =2870a(21) =3311a(22) =3971a(23) =4324a(24) =4914a(25) =5730a(26) =6201a(27) =6990a(28) =8000a(29) =8555