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 A051447 #26 Oct 08 2018 18:14:15 %S A051447 1,7,2228071,16888457,352978207,1737848873,77362855777,567442642711 %N A051447 Integers n such that 2^n == 9 (mod n). %C A051447 No other terms below 10^15. [_Max Alekseyev_, May 20 2012] %H A051447 Joe K. Crump, <a href="http://web.archive.org/web/20070614175509/http://www.immortaltheory.com/NumberTheory/2nmodn.htm">2^n mod n</a> %t A051447 m = 9; Join[Select[Range[m], Divisible[2^# - m, #] &], %t A051447 Select[Range[m + 1, 10^3], PowerMod[2, #, #] == m &]] (* _Robert Price_, Oct 08 2018 *) %Y A051447 Cf. A125000, A124974, A033983, A033982, A033981, A050259, A124977, A124965, A015911, A015910. %Y A051447 Cf. A033981, A033982, A033983. %K A051447 hard,nonn,more %O A051447 1,2 %A A051447 Joe K. Crump (joecr(AT)carolina.rr.com) %E A051447 Edited by _N. J. A. Sloane_, Jun 22 2008, at the suggestion of _Don Reble_ %E A051447 Terms 1, 7 prepended by _Max Alekseyev_, May 18 2011