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A129978
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Numbers k such that A120265(k) = numerator(Sum_{j=1..k} 1/j!) is a prime.
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0
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2, 3, 4, 5, 6, 7, 12, 16, 19, 21, 22, 25, 41, 114, 181, 236, 2003
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OFFSET
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1,1
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COMMENTS
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Corresponding primes are A120265(a(n)) = {3, 5, 41, 103, 1237, 433, 164611949, 35951249665217, 52255141388393, 43894318766250120011, 386270005143001056097, 53952693026046706215979, 1249584099900912571604389306768231303904375213027, ...}.
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LINKS
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MATHEMATICA
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Do[ f=Numerator[ Sum[ 1/k!, {k, 1, n} ] ]; If[ PrimeQ[f], Print[{n, f}] ], {n, 1, 236} ]
Flatten[Position[Numerator[Accumulate[1/Range[2150]!]], _?PrimeQ]] (* Harvey P. Dale, May 03 2013 *)
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PROG
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(PARI) t=0; for( n=1, 1000, if( ispseudoprime( numerator( t+=1/n!)), print( n", " ))) \\ M. F. Hasler, Jun 18 2007
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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