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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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2
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0, 1, 1, 3, 3, 20, 126, 694, 2874, 25059, 218517, 2054986, 21050226
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| Based on a question from Leroy Quet.
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EXAMPLE
| 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
| Cf. A078432, A078433.
Sequence in context: A157050 A059368 A090694 * A112534 A006656 A205452
Adjacent sequences: A078428 A078429 A078430 * A078432 A078433 A078434
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KEYWORD
| more,nonn
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AUTHOR
| Reiner Martin (reinermartin(AT)hotmail.com), Dec 30 2002
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EXTENSIONS
| a(11)-a(13) from Robert Gerbicz (robert.gerbicz(AT)gmail.com), Nov 27 2010
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