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 A219037 #23 Dec 28 2022 05:44:05 %S A219037 2,6,66,73786976294838206466 %N A219037 Numbers k such that k divides 2^k + 2 and (k-1) divides 2^k + 1. %C A219037 Also, numbers k such that 2^k == k-2 (mod k*(k-1)). %C A219037 The sequence is infinite: if m is in this sequence, then so is 2^m + 2. %C A219037 No other terms below 10^20. %D A219037 W. Sierpinski, 250 Problems in Elementary Number Theory. New York: American Elsevier, 1970. Problem #18. %H A219037 Kin Y. Li et al., <a href="http://www.math.ust.hk/excalibur/v14_n2.pdf">Solution to Problem 323</a>, Mathematical Excalibur 14(2), 2009, p. 3. %F A219037 Conjecture: a(n+1) = 2^a(n) + 2 for all n. %Y A219037 Intersection of A006517 and A055685. %Y A219037 Cf. A217468, A216822, A171959. %K A219037 nonn,hard,more %O A219037 1,1 %A A219037 _Max Alekseyev_, Nov 10 2012