A371656 Numbers k such that k - 2 and k + 2 have the same number of prime factors, counted with multiplicity.

5, 8, 9, 10, 12, 15, 21, 23, 24, 36, 37, 38, 39, 45, 53, 58, 60, 67, 68, 69, 81, 84, 86, 89, 93, 99, 100, 102, 105, 110, 111, 112, 113, 117, 120, 121, 129, 131, 134, 138, 143, 144, 154, 157, 165, 172, 173, 178, 184, 185, 188, 195, 203, 204, 207, 211, 215, 216, 217, 219, 225, 230, 231, 240, 244

Offset: 1

Author

Robert Israel, Apr 01 2024

Keywords

• nonn

Comments

Numbers k such that A001222(k - 2) = A001222(k + 2).

Examples

			a(4) = 10 is a term because 10 - 2 = 8 = 2^3 and 10 + 2 = 12 = 2^2 * 3 are both products of 3 primes, counted with multiplicity.
		

Links

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

Crossrefs

Cf. A001222. Contains A371622.

Programs

Maple

M:= map(numtheory:-bigomega, [$1..10^3]):
select(k -> M[k-2] = M[k+2], [$3 .. 10^3 - 2]);

Mathematica

Select[Range[3,245],PrimeOmega[#-2]==PrimeOmega[#+2]&] (* Stefano Spezia, Apr 01 2024 *)

Extensions

Suggested by Joerg Arndt