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Search: id:A109898
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| A109898 |
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a(n) = least integer of the form (n-2)(n-4)...(n-2k)/n. 0 if no such number exists. |
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+0
2
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| 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 40, 0, 0, 3003, 105, 0, 71680, 0, 24192, 2078505, 0, 0, 330, 4216455243, 0, 2788660875, 39536640, 0, 256256, 0, 16380, 6153560492625, 0, 276348105, 15841280, 0, 0, 20228646742486875, 1116288, 0, 1190707200, 0
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OFFSET
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1,8
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COMMENT
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a(n) = 0 if n = 1,9, p or 2*p, p is a prime. This is not exhaustive.
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EXAMPLE
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a(12) = 10*8*6/12 =40, a(15) = 13*11*9*7*5/15 =3003.
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PROGRAM
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(PARI) a(n) = pp=n-2; k=1; while((n-2*k>0) && ((pp % n)>0), k=k+1; pp=pp*(n-2*k)); if( ((pp%n)==0) && (pp>0), return(pp/n), return(0)); - Matthew Conroy Mar 28 2006
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CROSSREFS
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Cf. A109899.
Sequence in context: A057382 A007270 A057387 this_sequence A092573 A091009 A167163
Adjacent sequences: A109895 A109896 A109897 this_sequence A109899 A109900 A109901
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 13 2005
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EXTENSIONS
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More terms from Matthew Conroy Mar 28 2006
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