A339699 Numbers m such that 3^m-1 and 3^m+1 have the same number k of prime factors counted with multiplicity.

5, 23, 25, 31, 41, 43, 47, 53, 67, 101, 109, 113, 127, 137, 141, 149, 155, 187, 191, 195, 203, 209, 253, 275, 317, 322, 329, 367, 389, 409, 415, 503, 537, 565, 613, 623, 637, 643

Offset: 1

Author

Zak Seidov, Dec 14 2020

Keywords

• nonn
• more

Comments

Corresponding values of k: {3, 3, 5, 4, 4, 3, 4, 4, 4, 6, 9}.

Examples

			3^5 - 1 = 242 = 2*11*11, 3^5 + 1 = 244 =  2*2*61 (both are 3-almost primes (A110187)).
		

Crossrefs

Cf. A001222, A057941, A057958.

Programs

PARI

isok(m) = bigomega(3^m-1) == bigomega(3^m+1); \\ Michel Marcus, Dec 14 2020