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 A242959 #34 Jun 02 2020 16:02:09 %S A242959 2,20771,40487,41542,80974,83084,161948,643901,1255097,1287802, %T A242959 1391657,1931703,2510194,2575604,2783314,3765291,3863406,4174971, %U A242959 5020388,5151208,5566628,7530582,7726812,8349942,10040776,11133256,15061164,15308227,15453624,16699884 %N A242959 Numbers n such that 5^A000010(n) == 1 (mod n^2). %H A242959 Giovanni Resta, <a href="/A242959/b242959.txt">Table of n, a(n) for n = 1..479</a> (terms < 10^15, first 75 terms from Felix Fröhlich) %t A242959 Select[Range[167*10^5],PowerMod[5,EulerPhi[#],#^2]==1&] (* _Harvey P. Dale_, Jun 02 2020 *) %o A242959 (PARI) for(n=2, 10^9, if(Mod(5, n^2)^(eulerphi(n))==1, print1(n, ", "))) %Y A242959 Cf. A077816, A242958, A242960. %Y A242959 If a(n) is prime, then a(n) is in A123692. %K A242959 nonn %O A242959 1,1 %A A242959 _Felix Fröhlich_, May 27 2014