Project Euler Forum

I check what I did a long time ago.
I needed only primes under 10^6.
The 26th sqube is <removed by moderator>.
Hope this could help you.

uws8505 wrote: Tue Dec 09, 2008 4:13 am Is there any odd prime-proof sqube which contains the contiguous sub-string "200"?

DNS wrote: Tue Dec 09, 2008 7:26 amYes, there is

Could anyone post a number that ends with either 1 or 3 or 7 or 9 (i.e., one of those numbers is in its units place) that is prime-proof? It does not have to be a sqube let alone one that contains 200.

h_anand wrote: Wed May 02, 2018 11:09 pm Could anyone post a number that ends with either 1 or 3 or 7 or 9 (i.e., one of those numbers is in its units place) that is prime-proof? It does not have to be a sqube let alone one that contains 200.

If you've solved the problem, take a look at my post from 15 Jan 2018. I ran through the first 100,000 prime-proof 200-squbes, and found 6 that ended in 1, 3, 7, or 9 (3 ended with a 7, 1 each of the other 3 units digits). The first of those was the 10,701st prime-proof 200-sqube, 884352220050857. You could easily modify my code to just look for prime-proof numbers that aren't divisible by 2 or 5.

h_anand wrote: Wed May 02, 2018 11:09 pm
Could anyone post a number that ends with either 1 or 3 or 7 or 9 (i.e., one of those numbers is in its units place) that is prime-proof? It does not have to be a sqube let alone one that contains 200.

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