A290184 Numbers k such that k mod phi(k) = lambda(k).

20, 42, 100, 156, 272, 294, 342, 500, 660, 780, 1332, 1980, 2028, 2058, 2500, 3900, 4624, 5256, 5940, 6498, 7260, 9312, 10140, 11772, 12500, 14406, 17820, 19500, 21780, 26364, 26406, 37056, 49284, 50700, 53460, 62244, 62500, 65340, 65792, 78608, 79860, 97500

Offset: 1

Author

Thomas Ordowski, Jul 23 2017

Keywords

• nonn

Comments

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

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

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

Links

• Robert Israel, Table of n, a(n) for n = 1..184

Crossrefs

Subsequence of A124240.

Cf. A000010, A002322, A068494.

Programs

Maple

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

Mathematica

Select[Range[10^5], Mod[#, EulerPhi@ #] == CarmichaelLambda@ # &] (* Michael De Vlieger, Jul 23 2017 *)

PARI

isok(n) = (n % eulerphi(n)) == lcm(znstar(n)[2]); \\ Michel Marcus, Jul 23 2017

Extensions

More terms from Robert Israel, Jul 23 2017