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Numbers k such that k mod phi(k) = lambda(k).
1

%I #19 Jul 23 2021 02:08:36

%S 20,42,100,156,272,294,342,500,660,780,1332,1980,2028,2058,2500,3900,

%T 4624,5256,5940,6498,7260,9312,10140,11772,12500,14406,17820,19500,

%U 21780,26364,26406,37056,49284,50700,53460,62244,62500,65340,65792,78608,79860,97500

%N Numbers k such that k mod phi(k) = lambda(k).

%C Numbers k such that A068494(k) = A002322(k).

%C If k is in the sequence, then k*gpf(k) is in the sequence.

%C Are there infinitely many terms of the form (p-1)*p, where p is a prime?

%H Robert Israel, <a href="/A290184/b290184.txt">Table of n, a(n) for n = 1..184</a>

%p select(n -> n mod numtheory:-phi(n) = numtheory:-lambda(n), [seq(i,i=2..100000,2)]); # _Robert Israel_, Aug 04 2017

%t Select[Range[10^5], Mod[#, EulerPhi@ #] == CarmichaelLambda@ # &] (* _Michael De Vlieger_, Jul 23 2017 *)

%o (PARI) isok(n) = (n % eulerphi(n)) == lcm(znstar(n)[2]); \\ _Michel Marcus_, Jul 23 2017

%Y Subsequence of A124240.

%Y Cf. A000010, A002322, A068494.

%K nonn

%O 1,1

%A _Thomas Ordowski_, Jul 23 2017

%E More terms from _Robert Israel_, Jul 23 2017