a(n) = [x^n] exp(Sum_{k>=1} sigma(n*k)*x^k/k).

Terms

a(0) =1a(1) =1a(2) =8a(3) =39a(4) =385a(5) =917a(6) =31247a(7) =22527a(8) =1081986a(9) =2464860a(10) =50099635a(11) =14931071a(12) =19684696065a(13) =394805109a(14) =82267017929a(15) =496514888157a(17) =284625019799