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 A123061 #24 Aug 16 2021 21:30:29
%S A123061 1,2,22,77,242,371,16102,45727,73447,81286,112277,368237,10191797,
%T A123061 13563742,30958697,389974222,6171655457,55606837682,401469524477,
%U A123061 434715808966,1729670231597,12399384518278,28370781933478,32458602019394,45360785149757,1073804398767214
%N A123061 Numbers k that divide 5^k - 3.
%C A123061 Some larger terms: 10157607413638637338691, 678641208236297002873422185407157785099272404809011007522511134591325167. - _Max Alekseyev_, Oct 20 2016
%t A123061 Select[Range[1000000], IntegerQ[(PowerMod[5,#,# ]-3)/# ]&]
%t A123061 Do[If[IntegerQ[(PowerMod[5, n, n ]-3)/n], Print[n]], {n, 10^9}] (* _Ryan Propper_, Dec 30 2006 *)
%o A123061 (PARI) is(n)=Mod(5,n)^n==3 \\ _Charles R Greathouse IV_, Nov 04 2016
%Y A123061 Cf. A050259, A130422, A277554, A116629.
%Y A123061 Solutions to 5^n == k (mod n): A067946 (k=1), A015951 (k=-1), A124246 (k=2), A123062 (k=-2), this sequence (k=3), A123052 (k=-3), A125949 (k=4), A123047 (k=-4), A123091 (k=5), A015891 (k=-5), A277350 (k=6), A277348 (k=-6).
%K A123061 nonn
%O A123061 1,2
%A A123061 _Alexander Adamchuk_, Nov 04 2006
%E A123061 More terms from _Farideh Firoozbakht_, Nov 18 2006
%E A123061 Corrected and extended by _Ryan Propper_, Jan 01 2007
%E A123061 Entry revised by _N. J. A. Sloane_, Jan 24 2007
%E A123061 a(18) from _Lars Blomberg_, Dec 12 2011
%E A123061 a(19)-a(26) from _Max Alekseyev_, Oct 20 2016