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A263076
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Numbers n such that the fractional part of the sum of the first n primes (A007504) divided by n equals 1/2.
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1
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OFFSET
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1,1
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COMMENTS
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No other terms < 10^9.
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LINKS
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EXAMPLE
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a(1) = 2 since A007504(2) = 5 and 5/2 has a remainder of half of 2 which is 1.
a(2) = 1810 because A007504(1810) = 13150555 and 13150555/1810 = 14531/2.
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MATHEMATICA
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p = 2; k = s = 0; lst = {}; While[k < 100000001, s = s + p; If[ 2Mod[s, ++k] == k, AppendTo[lst, k]; Print[k]]; p = NextPrime@ p; k++]
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PROG
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(PARI) n=s=0; forprime(p=2, , s+=p; n++; if(n%2==0 && s%n == n/2, print1(n", "))) \\ Charles R Greathouse IV, Oct 09 2015
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CROSSREFS
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KEYWORD
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nonn,more,hard
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AUTHOR
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STATUS
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approved
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