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 A079543 #15 Aug 19 2025 22:56:54
%S A079543 74431,71528191,125780831,178708831,4150390625,68738591551,
%T A079543 171739186591,429079903231,634061169071
%N A079543 Numbers k such that k has at least two distinct prime factors and if a prime p divides k then (p-1) | (k-1) and (p+1) | (k+1).
%H A079543 Donovan Johnson, <a href="/A079543/a079543.txt">1384 terms > a(9)</a>
%e A079543 a(1) = 74431 = 7^4 * 31 because 6 and 30 divide 74430 and 8 and 32 divide 74432.
%t A079543 Do[ f = Transpose[ FactorInteger[n]][[1]]; If[ Length[f] > 1 && Union[ Mod[n - 1, f - 1]] == {0} && Union[ Mod[n + 1, f + 1]] == {0}, Print[n]], {n, 6, 10^10}]
%Y A079543 Intersection of A056729 and A080062, minus A001597.
%K A079543 nonn
%O A079543 1,1
%A A079543 _Don Reble_, Jan 22 2003
%E A079543 a(6)-a(7) from _Donovan Johnson_, Apr 09 2010
%E A079543 a(8)-a(9) from _Donovan Johnson_, Jan 21 2013