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Search: id:A067847
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| A067847 |
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Number of divisors d of n! such that d+1 is prime. |
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+0
3
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| 1, 2, 3, 5, 9, 15, 27, 40, 63, 100, 180, 248, 459, 696, 1019, 1299, 2495, 3219, 6011, 7986, 11247, 17029, 32567, 39501, 53017, 79775, 97251, 126981, 245675, 301054, 582853, 668274, 921616, 1382954, 1811949, 2097059, 4088346, 6142187, 8417004
(list; graph; listen)
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OFFSET
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1,2
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LINKS
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Ray Chandler, Table of n, a(n) for n=1..42
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FORMULA
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a(n) = A067513(A000142(n)).
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EXAMPLE
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a(5)=9 because the divisors of 5!=120 are 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 60 and 120 and the primes are 2, 3, 5, 7, 11, 13, 31, 41 and 61
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PROGRAM
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(PARI) a(n)=s=0; fordiv (n!, i, if(isprime(n!/i+1), s=s+1)); return(s);
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CROSSREFS
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Cf. A067513, A156190.
Sequence in context: A005169 A129852 A065954 this_sequence A022858 A090905 A065956
Adjacent sequences: A067844 A067845 A067846 this_sequence A067848 A067849 A067850
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 14 2002
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EXTENSIONS
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More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Mar 19 2002
More terms from Naohiro Nomoto (n_nomoto(AT)yabumi.com), Mar 13 2002
More terms from Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 26 2004
a(28)=118584 from Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 07 2004
Corrected a(28)=126981 and added a(29)-a(31) by Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 03 2009
a(32)-a(42) from Ray Chandler (rayjchandler(AT)sbcglobal.net), Feb 05 2009
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