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 A128647 #12 Feb 16 2025 08:33:05
%S A128647 1,1,3,7,41,3,53,437,5167,34189,36037,3833,3987,11521,274223,3458639,
%T A128647 103063291,100392623,34273501,33510453,308270747,302107667,
%U A128647 12626774467,12402802537,25216220279,124110148411,2142721739387,111888942151111
%N A128647 a(n) = numerator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)).
%C A128647 Numbers m such that A128648(m) = A128646(n) are listed in A128649.
%H A128647 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimeSums.html">Prime sums</a>
%F A128647 a(n) = numerator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1)).
%t A128647 Table[Numerator[Sum[(-1)^(k+1)*1/(Prime[k]-1),{k,1,n}]],{n,1,36}]
%Y A128647 Cf. A128648 (denominator(Sum_{k=1..n} (-1)^(k+1)/(prime(k)-1))).
%Y A128647 Cf. A120271 (numerator(Sum_{k=1..n} 1/(prime(k)-1))).
%Y A128647 Cf. A128646, A128649, A119686, A006093, A000040.
%K A128647 frac,nonn
%O A128647 1,3
%A A128647 _Alexander Adamchuk_, Mar 18 2007