A226368 Numbers k such that Omega(k) = Omega(2^k + 1), where Omega = A001222 is the number of prime factors counted with multiplicity.

2, 6, 36, 44, 52, 60, 72, 88, 112, 116, 136, 140, 152, 184, 288, 292, 320, 352, 388, 400, 404, 536, 544, 584, 632, 796, 844, 928, 1072, 1136

Offset: 1

Author

Irina Gerasimova, Jun 05 2013

Keywords

• nonn
• more
• hard

Comments

At the moment, the least candidate for a(31) is 1168 = 2^4 * 73; the entry for 2^1168 + 1 on factordb.com has 3 prime factors and 1 composite cofactor with 326 decimal digits. - Lucas A. Brown, Mar 19 2024

Crossrefs

Cf. A001222, A054992, A155900.

Programs

PARI

is(n)=bigomega(2^n+1)==bigomega(n) \\ Charles R Greathouse IV, Mar 18 2014

Formula

{k: A054992(k) = A001222(k)}.

Extensions

More terms from Jon E. Schoenfield, Sep 01 2013

a(29) added using factordb.com by Daniel Suteu, Jan 21 2023

a(30) added using factordb.com by Lucas A. Brown, Mar 19 2024