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Search: id:A078431
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| A078431 |
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Number of permutations p of 1,2,...,n such that both numerator and denominator of the continued fraction [p(1); p(2),...,p(n)] are primes. |
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3
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OFFSET
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1,4
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COMMENT
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Based on a question from Leroy Quet.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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a(4)=3 because [2;1,3,4]=47/17, [2;3,1,4]=43/19, [4;3,1,2]=47/11
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CROSSREFS
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Cf. A078432, A078433.
Adjacent sequences: A078428 A078429 A078430 this_sequence A078432 A078433 A078434
Sequence in context: A157050 A059368 A090694 this_sequence A112534 A006656 A159910
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KEYWORD
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more,nonn
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AUTHOR
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Reiner Martin (reinermartin(AT)hotmail.com), Dec 30 2002
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