O.g.f.: exp( Sum_{n>=1} A067692(n)*x^n/n ), where A067692(n) = [sigma(n)^2 + sigma(n,2)]/2.

Terms

a(0) =1a(1) =1a(2) =4a(3) =8a(4) =21a(5) =39a(6) =93a(7) =171a(8) =364a(9) =675a(10) =1338a(11) =2433a(12) =4641a(13) =8282a(14) =15222a(15) =26811a(16) =47920a(17) =83046a(18) =145288a(19) =248164a(20) =425970a(21) =718303a(22) =1213106a(23) =2020540a(24) =3365352a(25) =5541996a(26) =9115640a(27) =14856657a(28) =24164430a(29) =39002462