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 A180061 #19 Jun 27 2024 22:16:04 %S A180061 5,6,7,9,11,12,13,17,19,21,23,29,31,37,41,43,47,53,59,61,63,67,71,73, %T A180061 79,83,89,97,101,103,107,109,113,121,127,131,133,137,139,149,151,157, %U A180061 163,167,172,173,179,181,190,191,193,196,197,199,211 %N A180061 Numbers k such that (2^(2^k mod k) mod k) = 4. %C A180061 The composite terms in this sequence start 6, 9, 12, 21, 63, 121, 133, 172, 190, 196, ... - _R. J. Mathar_, Jan 14 2011 %H A180061 Harvey P. Dale, <a href="/A180061/b180061.txt">Table of n, a(n) for n = 1..1000</a> %F A180061 A180060(a(n)) = 4. %t A180061 Select[Range[300],PowerMod[2,PowerMod[2,#,#],#]==4&] (* _Harvey P. Dale_, Sep 08 2016 *) %o A180061 (PARI) s=[]; for(n=1, 1000, if((2^(2^n%n)%n)==4, s=concat(s, n))); s \\ _Colin Barker_, Jun 27 2014 %Y A180061 Cf. A000040, A000079, A179976, A180060. %K A180061 nonn %O A180061 1,1 %A A180061 _Juri-Stepan Gerasimov_, Jan 14 2011 %E A180061 Terms corrected by _R. J. Mathar_, Jan 14 2011