G.f.: A(x) = exp( Sum_{n>=1} sigma(n)^4 * x^n/n ).

Terms

a(0) =1a(1) =1a(2) =41a(3) =126a(4) =1526a(5) =5185a(6) =46920a(7) =176865a(8) =1254608a(9) =4986548a(10) =30563031a(11) =123868761a(12) =683127011a(13) =2793828323a(14) =14223836013a(15) =58127497582a(16) =278433541834