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
Keywords
Examples
1283 is in the sequence because phi(phi(1283)) = lambda(lambda(1283)) = 640.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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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:
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Mathematica
Select[Range[1000], EulerPhi[EulerPhi[#]] == CarmichaelLambda[CarmichaelLambda[#]] &] (* Amiram Eldar, Aug 19 2019 *)