A179401 Numbers k such that phi(phi(k)) = lambda(lambda(k)).

1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 14, 18, 19, 22, 23, 27, 38, 46, 47, 54, 59, 81, 83, 94, 107, 118, 162, 163, 166, 167, 179, 214, 227, 243, 251, 263, 326, 334, 347, 358, 359, 383, 454, 467, 479, 486, 487, 502, 503, 526, 563, 587, 694, 718, 719, 729, 766, 839, 863, 887, 934, 958

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

1283 is in the sequence because phi(phi(1283)) = lambda(lambda(1283)) = 640.

Maple

with(numtheory): for n from 1 to 1500 do: x:=phi(n):y:=lambda(n):if phi(x)=lambda(y)
  then printf(`%d, `, n):else fi:od:

Mathematica

Select[Range[1000], EulerPhi[EulerPhi[#]] == CarmichaelLambda[CarmichaelLambda[#]] &] (* Amiram Eldar, Aug 19 2019 *)

Crossrefs

Cf. A000010, A002322.

Sequence in context: A071557 A331802 A271108 * A117729 A073726 A194125

Adjacent sequences: A179398 A179399 A179400 * A179402 A179403 A179404

Keyword

nonn

Author

Michel Lagneau, Jan 07 2011

Status

approved