a(n) = Sum_{i+j+k=n, i,j,k >= 1} sigma(i) * sigma(j) * sigma(k).

Terms

a(0) =0a(1) =0a(2) =1a(3) =9a(4) =39a(5) =120a(6) =300a(7) =645a(8) =1261a(9) =2262a(10) =3825a(11) =6160a(12) =9471a(13) =14178a(14) =20376a(15) =28965a(16) =39600a(17) =54066a(18) =71145a(19) =94248a(20) =120140a(21) =155310a(22) =193116a(23) =244560a(24) =297819a(25) =370860a(26) =443710a(27) =544554a(28) =641655a(29) =778458