a(0) = 1, a(n) = 20*sigma[3](n).

Terms

a(0) =1a(1) =20a(2) =180a(3) =560a(4) =1460a(5) =2520a(6) =5040a(7) =6880a(8) =11700a(9) =15140a(10) =22680a(11) =26640a(12) =40880a(13) =43960a(14) =61920a(15) =70560a(16) =93620a(17) =98280a(18) =136260a(19) =137200a(20) =183960a(21) =192640a(22) =239760a(23) =243360a(24) =327600a(25) =315020a(26) =395640a(27) =408800a(28) =502240a(29) =487800