L.g.f.: Sum_{n>=1} a(n)*x^n/n = Sum_{n>=1} x^n/n * exp( Sum_{k>=1} sigma(n*k)*x^(n*k)/k ).

Terms

a(0) =1a(1) =3a(2) =7a(3) =19a(4) =26a(5) =75a(6) =78a(7) =211a(8) =241a(9) =518a(10) =463a(11) =1447a(12) =1002a(13) =2558a(14) =2612a(15) =5715a(16) =3928a(17) =11901a(18) =7316a(19) =21574a(20) =17031a(21) =35159a(22) =23047a(23) =80575a(24) =40951a(25) =108488a(26) =86911a(27) =206638a(28) =107823a(29) =370220