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 A387404 #12 Aug 29 2025 20:54:45
%S A387404 325,637,925,1525,1573,1813,1825,2425,2725,2989,3577,3757,3925,4477,
%T A387404 4525,4693,4753,4825,5341,5725,6025,6253,6877,6925,7381,7693,7825,
%U A387404 8125,8425,8725,8833,8869,9325,9457,9925,10225,10309,10525,10693,10825,10933,11221,11425,11737,11809,12337,12493,13189,13357,13525,13573
%N A387404 Numbers of the form 12*k + 1 that satisfy Euler's condition for odd perfect numbers (A228058).
%H A387404 Antti Karttunen, <a href="/A387404/b387404.txt">Table of n, a(n) for n = 1..10000</a>
%t A387404 nn = 51; n = 1; t = {}; While[Length[t] < nn, n = n + 2; {p, e} = Transpose[FactorInteger[n]]; od = Select[e, OddQ]; If[Length[e] > 1 && Length[od] == 1 && Mod[od[[1]], 4] == 1 && Mod[p[[Position[e, od[[1]]][[1, 1]]]], 4] == 1&&Mod[n,12]==1, AppendTo[t, n]]]; t (* _James C. McMahon_, Aug 29 2025 *)
%o A387404 (PARI) is_A387404(n) = if(1!=(n%12) || (omega(n)<2), 0, my(f=factor(n), y=0); for(i=1, #f~, if(1==(f[i, 2]%4), if((1==y)||(1!=(f[i, 1]%4)), return(0), y=1), if(f[i, 2]%2, return(0)))); (y));
%Y A387404 Intersection of A017533 and A228058.
%K A387404 nonn,new
%O A387404 1,1
%A A387404 _Antti Karttunen_, Aug 29 2025