mersenneforum.org - Mistake in List of Primes

mersenneforum.org (https://www.mersenneforum.org/index.php)

- Sierpinski/Riesel Base 5 (https://www.mersenneforum.org/forumdisplay.php?f=54)

- - Mistake in List of Primes (https://www.mersenneforum.org/showthread.php?t=7184)

rogue

2007-02-22 22:53

I just discovered that 137132*5^25323+1 is composite. I assume that a couple of digits in the exponent were transposed, but haven't retested the k.

BTW, I've verified all other Sierpinki and Riesel base 5 candidates for n > 100 with Phil's phrot program. This one showed up as composite while I was testing. It also shows as composite with PFGW.

thommy

2007-02-23 00:35

[quote=rogue;99194]I just discovered that 137132*5^25323+1 is composite. I assume that a couple of digits in the exponent were transposed...[/quote]

You were right. Sieved that k from 20000 to 27000 for 1 minute and looked at close matches:

Primality testing 137132*5^25353+1 [N-1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 2
Calling Brillhart-Lehmer-Selfridge with factored part 99.97%
137132*5^25353+1 is prime! (98.3633s+0.0211s)

All times are UTC. The time now is 09:35.