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

1,1

Comments

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

Links

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

Example

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.

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 *)

Crossrefs

Cf. A001222. Contains A371622.

Sequence in context: A300331 A293271 A348046 * A323215 A334818 A337215

Adjacent sequences: A371653 A371654 A371655 * A371657 A371658 A371659

Keyword

nonn

Author

Robert Israel, Apr 01 2024

Extensions

Suggested by Joerg Arndt

Status

approved