This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A339721 #5 Dec 14 2020 16:01:07
%S A339721 1,-6,-6,15,-6,30,-6,-26,15,30,-6,-60,-6,30,30,51,-6,-60,-6,-60,30,30,
%T A339721 -6,96,15,30,-26,-60,-6,-114,-6,-102,30,30,30,96,-6,30,30,96,-6,-114,
%U A339721 -6,-60,-60,30,-6,-210,15,-60,30,-60,-6,96,30,96,30,30,-6,156,-6,30,-60,172,30
%N A339721 Dirichlet g.f.: Product_{k>=2} 1 / (1 + k^(-s))^6.
%F A339721 a(1) = 1; a(n) = -Sum_{d|n, d < n} A339338(n/d) * a(d).
%F A339721 a(p^k) = A022601(k) for prime p.
%Y A339721 Cf. A022601, A316441, A339338, A339717, A339718, A339719, A339720, A339722.
%K A339721 sign
%O A339721 1,2
%A A339721 _Ilya Gutkovskiy_, Dec 14 2020