%I #19 Sep 08 2022 08:45:05

%S 2,3,6,9,11,14,15,18,21,23,27,29,33,42,47,51,53,54,57,69,71,73,74,81,

%T 82,86,95,101,105,111,113,114,115,121,129,130,138,141,142,165,167,169,

%U 179,181,199,203,209,213,230,233,235,243,250,255,258,277,279,306,307

%N Numbers k such that 2^k+1 and 2^k-1 have the same number of distinct prime factors.

%C Numbers k such that omega(2^k+1) = omega(2^k-1).

%H Amiram Eldar, <a href="/A067886/b067886.txt">Table of n, a(n) for n = 1..141</a>

%t sndpQ[n_]:=Module[{c=2^n},PrimeNu[c+1]==PrimeNu[c-1]]; Select[Range[ 250], sndpQ] (* _Harvey P. Dale_, Feb 04 2016 *)

%o (PARI) isok(k) = omega(2^k-1) == omega(2^k+1); \\ _Michel Marcus_, Feb 13 2020

%o (Magma) [k: k in [2..307] | #PrimeDivisors(2^k-1) eq #PrimeDivisors(2^k+1) ]; // _Marius A. Burtea_, Feb 13 2020

%Y Cf. A001221, A046799, A046800.

%K nonn

%O 1,1

%A _Benoit Cloitre_, Mar 02 2002

%E More terms from _Rick L. Shepherd_, May 14 2002

%E More terms from _Amiram Eldar_, Feb 13 2020