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A116896
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Numbers k such that k! + k!! + 1 is prime, where k!! denotes double factorial (A001147).
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1
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OFFSET
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1,3
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COMMENTS
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1976! + 1976!! + 1 is a 5657-digit prime. Next term is greater than 4000.
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LINKS
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Table of n, a(n) for n=1..8.
Joe McLean, Interesting Sources of Probable Primes
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EXAMPLE
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6! + 6!! + 1 = 769, which is prime.
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CROSSREFS
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Cf. A000142, A001147, A116897.
Sequence in context: A179330 A066864 A181737 * A061062 A270141 A294349
Adjacent sequences: A116893 A116894 A116895 * A116897 A116898 A116899
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KEYWORD
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hard,more,nonn
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AUTHOR
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Giovanni Resta, Mar 04 2006
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EXTENSIONS
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5126 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
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STATUS
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approved
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