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A122151
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Indices n such that A122150[n] is a prime.
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3
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OFFSET
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1,1
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COMMENTS
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A122150[n] = Numerator[ Sum[ (-1)^(k+1) * 1/2^Prime[k], {k,1,n} ] ] begins {1,1,5,19,305,1219,19505,78019,1248305,79891519,319566077,20452228927, 327235662833,...}. Primes in A122150[n] are listed in A122152[n] = {5,19,327235662833,...}.
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LINKS
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FORMULA
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MATHEMATICA
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Do[f=Numerator[Sum[(-1)^(k+1)*1/2^Prime[k], {k, 1, n}]]; If[PrimeQ[f], Print[{n, f}]], {n, 1, 1000}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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