a(n) = sigma_2(n)*sigma_3(n)/sigma(n).

Terms

a(0) =1a(1) =15a(2) =70a(3) =219a(4) =546a(5) =1050a(6) =2150a(7) =3315a(8) =5299a(9) =8190a(10) =13542a(11) =15330a(12) =26690a(13) =32250a(14) =38220a(15) =51491a(16) =79170a(17) =79485a(18) =124166a(19) =119574a(20) =150500a(21) =203130a(22) =268710a(23) =232050a(24) =330771a(25) =400350a(26) =419020a(27) =470850a(28) =684546a(29) =573300