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 A273727 #19 Jun 29 2024 16:44:03 %S A273727 1,175952,348880,649078,951625,1495472,1944320,3140852,3483200, %T A273727 3643270,4359040,4703776,6513584,8170904,9854200,11005568,11831890, %U A273727 12149872,12828200,12910928,18095630,18964400,22034516,43599424,62849024,66322480,82159588,85181600 %N A273727 Numbers k such that 3k - 1 divides 3^k - 1 and 3 does not divide k. %t A273727 Select[Range[10^6], Mod[#,3] > 0 && PowerMod[3, #, 3*#-1] == 1 &] (* _Giovanni Resta_, May 29 2016 *) %o A273727 (PARI) is(n)=n%3 && Mod(3,3*n-1)^n==1 \\ _Charles R Greathouse IV_, May 29 2016 %Y A273727 Cf. A233415. Subsequence of A273614. %K A273727 nonn %O A273727 1,2 %A A273727 _Juri-Stepan Gerasimov_, May 28 2016