G.f.: exp( Sum_{n>=1} (2*sigma(n^2) - sigma(n)^2) * x^n/n ).

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =11a(5) =22a(6) =40a(7) =72a(8) =123a(9) =215a(10) =363a(11) =605a(12) =991a(13) =1618a(14) =2598a(15) =4139a(16) =6537a(17) =10229a(18) =15871a(19) =24476a(20) =37487a(21) =56995a(22) =86177a(23) =129531a(24) =193662a(25) =287992a(26) =426254a(27) =627841a(28) =920708a(29) =1344331