a(n) = Sum_{k=1..n-1} sigma_2(k) * sigma_3(n-k).

Terms

a(0) =0a(1) =1a(2) =14a(3) =83a(4) =324a(5) =986a(6) =2484a(7) =5625a(8) =11304a(9) =21596a(10) =37824a(11) =64746a(12) =103252a(13) =163536a(14) =244200a(15) =364855a(16) =517478a(17) =741087a(18) =1009244a(19) =1394080a(20) =1842690a(21) =2470668a(22) =3178188a(23) =4171260a(24) =5242610a(25) =6735966a(26) =8331338a(27) =10511692a(28) =12777898a(29) =15922212