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 A290184 #19 Jul 23 2021 02:08:36 %S A290184 20,42,100,156,272,294,342,500,660,780,1332,1980,2028,2058,2500,3900, %T A290184 4624,5256,5940,6498,7260,9312,10140,11772,12500,14406,17820,19500, %U A290184 21780,26364,26406,37056,49284,50700,53460,62244,62500,65340,65792,78608,79860,97500 %N A290184 Numbers k such that k mod phi(k) = lambda(k). %C A290184 Numbers k such that A068494(k) = A002322(k). %C A290184 If k is in the sequence, then k*gpf(k) is in the sequence. %C A290184 Are there infinitely many terms of the form (p-1)*p, where p is a prime? %H A290184 Robert Israel, <a href="/A290184/b290184.txt">Table of n, a(n) for n = 1..184</a> %p A290184 select(n -> n mod numtheory:-phi(n) = numtheory:-lambda(n), [seq(i,i=2..100000,2)]); # _Robert Israel_, Aug 04 2017 %t A290184 Select[Range[10^5], Mod[#, EulerPhi@ #] == CarmichaelLambda@ # &] (* _Michael De Vlieger_, Jul 23 2017 *) %o A290184 (PARI) isok(n) = (n % eulerphi(n)) == lcm(znstar(n)[2]); \\ _Michel Marcus_, Jul 23 2017 %Y A290184 Subsequence of A124240. %Y A290184 Cf. A000010, A002322, A068494. %K A290184 nonn %O A290184 1,1 %A A290184 _Thomas Ordowski_, Jul 23 2017 %E A290184 More terms from _Robert Israel_, Jul 23 2017