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 A109898 a(n) is the least integer of the form (n-2)(n-4)...(n-2k)/n. 0 if no such number exists. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,8 COMMENTS a(n) = 0 if n = 1,9, p or 2*p, p is a prime. This is not exhaustive. LINKS Table of n, a(n) for n=1..43. EXAMPLE a(12) = 10*8*6/12 = 40, a(15) = 13*11*9*7*5/15 = 3003. PROG (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 CROSSREFS Cf. A109899. Sequence in context: A007270 A222896 A057387 * A223074 A192732 A092573 Adjacent sequences: A109895 A109896 A109897 * A109899 A109900 A109901 KEYWORD nonn AUTHOR Amarnath Murthy, Jul 13 2005 EXTENSIONS More terms from Matthew Conroy, Mar 28 2006 STATUS approved

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Last modified September 11 17:54 EDT 2024. Contains 375839 sequences. (Running on oeis4.)