mersenneforum.org primes p(n-1) dividing the sum 2+3+5+7+...+p(n)
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 2019-03-26, 07:09 #1 enzocreti   Mar 2018 17·31 Posts primes p(n-1) dividing the sum 2+3+5+7+...+p(n) with Pari Gp i found that up to 10^10 there are only two primes 7 and 8263 of this type. infact 2+3+5+7+11=28 divisibile by 7. and 2+3+5+7+...+8269 divisibile by 8263. the heuristic says that there should be infinitely many of these primes but because the heuristic says loglog(n) they should be very rare. could somebody find onother such prime >10^10?
 2019-03-26, 09:07 #2 enzocreti   Mar 2018 17·31 Posts https://oeis.org/A078721 7 and 8263 belong to the Oeis sequence https://oeis.org/A078721 2 3 5 7 11 13 they are on the left side of this Tarrtaglia triangle made with primes

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