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 A074763 #7 May 23 2019 09:39:06
%S A074763 2,1,4,4,8,10,20,34,60,100,188,348,632,1162,2192,4114,7712,14542,
%T A074763 27596,52480,99880,190558,364724,699248,1342184,2580796,4971068,
%U A074763 9587560,18512792,35790376,69273668,134219794,260301176,505286416,981706832
%N A074763 a(n) = (1/n) * Sum_{d divides n} (-1)^(n+d)*phi(n/d)*2^d.
%F A074763 G.f.: Sum_{k>=1} phi(k)*log(1/(1 + 2*(-x)^k))/k. - _Ilya Gutkovskiy_, May 23 2019
%Y A074763 Cf. A000010, A000031, A038063.
%K A074763 nonn
%O A074763 1,1
%A A074763 _Vladeta Jovovic_, Sep 06 2002