G.f.: exp( Sum_{n>=1} A174468(n)*x^n/n ) where A174468(n) = Sum_{d|n} d*sigma(n/d)*sigma(d).

Terms

a(0) =1a(1) =1a(2) =5a(3) =10a(4) =31a(5) =58a(6) =157a(7) =299a(8) =711a(9) =1367a(10) =2987a(11) =5679a(12) =11807a(13) =22117a(14) =44006a(15) =81513a(16) =156885a(17) =286413a(18) =537058a(19) =967367a(20) =1773882a(21) =3155223a(22) =5677183a(23) =9976095a(24) =17661695a(25) =30682683a(26) =53544796a(27) =92037152a(28) =158575796a(29) =269850363