I was testing k = 1281979 for n<= 100000 and interestingly the first 10 n for which this is prime are prime themselves. After that unfortunately there's n = 1005 which obviously isn't. But the ratio of n being prime vs being composite continues to be very high for the remainder of the range.
Is that a known property of some k and is it known why it happens? Is there a connection to Mersenne?
Nothing like that on the Proth side, but there the n that yield primes seem to come in pairs of two that are close to each other (510% difference). Though it might just be the brain's inbuild pattern recognition going overboard. So I'll keep testing. If there's something the next n should be in the 3e5 range. ;)
Last fiddled with by bur on 20200908 at 05:41
