A392386 Numbers k such that omega(2*k) = omega(k + 2), where omega = A001221.

1, 2, 10, 12, 13, 18, 19, 20, 22, 24, 26, 31, 34, 36, 37, 38, 43, 44, 46, 48, 49, 50, 52, 53, 54, 56, 61, 67, 72, 73, 74, 80, 83, 86, 89, 92, 94, 96, 97, 98, 104, 106, 109, 113, 116, 121, 122, 127, 130, 131, 134, 138, 139, 142, 144, 146, 151, 154, 157, 158, 160, 162, 164, 168, 169

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

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

Maple

filter:= proc(k) NumberTheory:-Omega(2*k, distinct) = NumberTheory:-Omega(k+2, distinct) end proc:
select(filter, [$1..1000]); # Robert Israel, May 14 2026

Mathematica

Select[Range[200], PrimeNu[2*#] == PrimeNu[# + 2] &] (* Amiram Eldar, Jan 09 2026 *)

Prog

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

Crossrefs

Includes A307533. Cf. A001221, A006049.

Sequence in context: A300907 A327793 A276103 * A101222 A349831 A079252

Adjacent sequences: A392383 A392384 A392385 * A392387 A392388 A392389

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jan 09 2026

Status

approved