A067883 - OEIS

%I #31 Aug 10 2024 22:34:27

%S 1,2,4,6,8,12,48,60,72,96,128,240,432,480,720,1728,2016,6912,10368,

%T 14080,32768,142560,184320,196560,712800,1140480,1190400,1658880,

%U 1801800,3345408,3571200,5702400,6220800,8363520,10222080,10368000,14859936,29719872,50319360

%N Numbers k such that k = phi(sigma(phi(sigma(k)))).

%C This sequence has both terms of cycles of length 2 when iterating k <-phi(sigma(k)) (see A373435) plus cycles of length 1 (see A001229). - _Jud McCranie_, Aug 09 2024

%t Select[Range[10^6], EulerPhi[DivisorSigma[1, EulerPhi[DivisorSigma[1, #]]]] == # &] (* _Amiram Eldar_, Apr 24 2022 *)

%Y Cf. A000010, A000203, A062401, A163372.

%Y Supersequence of A001229. A373435 is a subsequence of this sequence.

%K easy,nonn

%O 1,2

%A _Benoit Cloitre_, Mar 02 2002

%E More terms from _Reiner Martin_, Jul 09 2002

%E a(35)-a(39) from _Amiram Eldar_, Apr 24 2022