a(n) = n! * Sum_{k=1..n} sigma_0(k)/k.

Terms

a(0) =1a(1) =4a(2) =16a(3) =82a(4) =458a(5) =3228a(6) =24036a(7) =212448a(8) =2032992a(9) =21781440a(10) =246853440a(11) =3201742080a(12) =42580650240a(13) =621037186560