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 A081116 #20 May 15 2022 07:30:24 %S A081116 5,29,42,75,132,134,140,152,159,162,163,201,206,215,241,256,277,301, %T A081116 314,347,404,406,412,424,431,434,435,473,478,487,513,528,549,573,586, %U A081116 619,676,678,684,696,703,706,707,745,750,759,785,800,821,845,858,891,948 %N A081116 Numbers k such that 17 divides 3^k-k. %C A081116 Suggested by a problem in a web page by Hojoo Lee entitled "Challenging problems in number theory". However, the page no longer exists. %H A081116 Amiram Eldar, <a href="/A081116/b081116.txt">Table of n, a(n) for n = 1..10000</a> %H A081116 <a href="/index/Rec#order_16">Index entries for linear recurrences with constant coefficients</a>, signature (2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-2,2,-1). %F A081116 a(n+1)-a(n) is the 16-periodic sequence (24, 13, 33, 57, 2, 6, 12, 7, 3, 1, 38, 5, 9, 26, 15, 21). %t A081116 Select[Range[1000], PowerMod[3, #, 17] == Mod[#, 17] &] (* _Amiram Eldar_, May 14 2022 *) %o A081116 (PARI) isok(n) = Mod(3, 17)^n == Mod(n, 17); \\ _Michel Marcus_, Dec 02 2013 %Y A081116 Cf. A024024 (3^n-n). %K A081116 nonn %O A081116 1,1 %A A081116 _Benoit Cloitre_, Apr 16 2003