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 A138907 #8 Jun 23 2025 22:20:17
%S A138907 2,14,2,74,32,2,2,-94,-52,482,-262,578,2,590,452,386,-814,326,1598,
%T A138907 1202,758,530,-1516,290,602,-154,-1618,2354,2612,1442,2420,-3646,794,
%U A138907 1430,1472,-862,-220,1142,938,2642,-2458,3782,4130,3698,1622,5798,3386,-3742,2,6002,-8566,-1246,2864,3566,1322,2690,3764
%N A138907 a(n) = A138906(n) - A138905(n).
%t A138907 a138906[n_]:=Module[{p=1,cnt=0},Until[cnt==n,If[Mod[Prime[p],6n]==1,cnt++];p++];Prime[p-1]];a138905[n_]:=Module[{p=1,cnt=0},Until[cnt==n,If[Mod[Prime[p],6n]==6n-1,cnt++];p++];Prime[p-1]];Table[a138906[n]-a138905[n],{n,57}] (* _James C. McMahon_, Jun 23 2025 *)
%Y A138907 Cf. A138905, A138906.
%K A138907 sign
%O A138907 1,1
%A A138907 _Zak Seidov_, Apr 03 2008
%E A138907 a(41) corrected by _James C. McMahon_, Jun 23 2025