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 A073099 #21 May 19 2022 10:53:11
%S A073099 1,31,12307,1180906852403,4726403852635437852230311,
%T A073099 26387151472737581442533784610190235872453672267436617,
%U A073099 16379090991119093215568426722482532968867795792384100101494022155108529793899838205018451949281878220687877
%N A073099 Numerator of b(n) = n * Sum_{k=2^n..2^(n+1)-1} (-1)^k/k.
%H A073099 Amiram Eldar, <a href="/A073099/b073099.txt">Table of n, a(n) for n = 1..10</a>
%H A073099 G. Vacca, <a href="https://books.google.fr/books?id=Q4qXAAAAMAAJ&hl=fr&pg=PA363#v=onepage&q&f=false">A new series for the Eulerian constant gamma=.577...</a>, Quart. J. Pure Appl. Math., Vol. 41 (1910), pp. 363-368.
%F A073099 Sum_{k>=1} b(k) = gamma = 0.5772... (A001620).
%e A073099 The fractions begin with 1/6, 31/210, 12307/120120, 1180906852403/18050444111700, ...
%t A073099 a[n_] := Numerator[n * Sum[(-1)^k/k, {k, 2^n, 2^(n+1)-1}]]; Array[a, 7] (* _Amiram Eldar_, May 19 2022 *)
%o A073099 (PARI) a(n)=numerator( n*sum(k=2^n,2^(n+1)-1,(-1)^k/k))
%Y A073099 Cf. A001620, A073100 (denominators).
%K A073099 easy,frac,nonn
%O A073099 1,2
%A A073099 _Benoit Cloitre_, Aug 18 2002