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A264858
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Integers k such that A007504(k) + 1 is a square.
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1
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OFFSET
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1,2
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COMMENTS
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Integers k such that the sum of the first k primes + 1 is a square.
Integers k such that A014284(k+1) is a square.
In A110996, it is commented that a(6) > 250000, if it exists.
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LINKS
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EXAMPLE
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a(2) = 17 because A007504(17) + 1 = 440 + 1 = 441 is a square.
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MATHEMATICA
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Join[{0}, Position[Accumulate[Prime[Range[6500]]]+1, _?(IntegerQ[Sqrt[ #]]&)]] // Flatten (* Harvey P. Dale, Feb 12 2018 *)
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PROG
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(PARI) lista(nn) = { print1(0, ", "); s = 1; for(k=1, nn, s += prime(k); if(issquare(s), print1(k, ", ")); ); }
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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