Re:Emirp Primes
by pmiller2 on Friday May 03, 2019 @01:36AM
(#19815845)
Sounds like just a bit of fun to me. For one, emirp-hood depends on the number base, which means it’s not intrinsic to the number, but depends on some arbitrary choice of representation. Generally, things like that don’t indicate anything deep.
Re:Emirp Primes
by emirp on Friday May 03, 2019 @03:59AM
(#19816438)
I can think of a couple of things off the top of my head:
- You can reject numbers that start with 2,4,5,6 or 8 since their reverse won't be prime.
- If you're searching through a range of numbers for emirps avoid checking for the same pair twice. For example if you start at 1 and check for emirps, by the time you're checking 311 you've already checked 113 so you don't need to check 311.
:D
[1] https://oeis.org/A006567
[2] https://oeis.org/A080790
Fractional bases, negative bases, negative fractional bases, base e (supposed to be optimal IIRC), perhaps complex bases, summat weirder?
https://en.wikipedia.org/wiki/Decimal
- You can reject numbers that start with 2,4,5,6 or 8 since their reverse won't be prime.
- If you're searching through a range of numbers for emirps avoid checking for the same pair twice. For example if you start at 1 and check for emirps, by the time you're checking 311 you've already checked 113 so you don't need to check 311.
[0] https://en.wikipedia.org/wiki/Palindromic_prime
See also: http://www.cadaeic.net/silopolis.htm