A392386 - OEIS

%I #17 May 16 2026 05:16:38

%S 1,2,10,12,13,18,19,20,22,24,26,31,34,36,37,38,43,44,46,48,49,50,52,

%T 53,54,56,61,67,72,73,74,80,83,86,89,92,94,96,97,98,104,106,109,113,

%U 116,121,122,127,130,131,134,138,139,142,144,146,151,154,157,158,160,162,164,168,169

%N Numbers k such that omega(2*k) = omega(k + 2), where omega = A001221.

%H Robert Israel, <a href="/A392386/b392386.txt">Table of n, a(n) for n = 1..10000</a>

%e 10 is a term because omega(20) = omega(12).

%p filter:= proc(k) NumberTheory:-Omega(2*k,distinct) = NumberTheory:-Omega(k+2,distinct) end proc:

%p select(filter, [$1..1000]); # _Robert Israel_, May 14 2026

%t Select[Range[200], PrimeNu[2*#] == PrimeNu[# + 2] &] (* _Amiram Eldar_, Jan 09 2026 *)

%o (Magma) [k: k in [1..170] | #PrimeDivisors(2*k) eq #PrimeDivisors(k + 2)];

%Y Includes A307533. Cf. A001221, A006049.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Jan 09 2026