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 A119723 #6 Feb 16 2025 08:33:01
%S A119723 1,3,13,113,2861,709,45601,408809,49595489,2426258561,485934733,
%T A119723 485460413,2429223061,2427480661,1284905668069,217047437215261,
%U A119723 182605590283392901,36508279615059377,36518889897389297
%N A119723 Numerator of Sum[ (-1)^(k-1) * 1/(Prime[k]-1)^2, {k,1,n}].
%H A119723 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimeSums.html">Prime Sums</a>.
%F A119723 a(n) = numerator[ Sum[ (-1)^(k-1) * 1/(Prime[k]-1)^2, {k,1,n}]].
%t A119723 Numerator[Table[Sum[(-1)^(i-1)*1/(Prime[i]-1)^2, {i, 1, n}], {n, 1, 30}]]
%Y A119723 Cf. A119686, A006093, A000040, A086242.
%K A119723 frac,nonn
%O A119723 1,2
%A A119723 _Alexander Adamchuk_, Jun 13 2006