A064186 Numbers n such that n!+1 and n!-1 have the same number of prime divisors (with repetition).

3, 5, 8, 9, 10, 13, 17, 20, 22, 24, 26, 34, 39, 53, 59, 61, 63, 69, 70, 76, 80, 87, 97, 99, 103, 124, 130

Offset: 1

Author

Jason Earls, Sep 20 2001

Keywords

• more
• nonn

Comments

200, 236, 392 and 634 are terms. - Chai Wah Wu, Jan 03 2020

Crossrefs

Cf. A054990, A054991.

Programs

Mathematica

Select[Range[30], PrimeOmega[#! - 1] == PrimeOmega[#! + 1] &] (* Amiram Eldar, Dec 01 2019 *)

PARI

for(n=2,100, if(bigomega(n!+1)==bigomega(n!-1),print(n)))

Extensions

a(15)-a(25) from Donovan Johnson, Mar 09 2008

Offset corrected by Donovan Johnson, Jul 11 2013

a(26)-a(27) from Amiram Eldar, Dec 01 2019