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A109898 a(n) = 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 May 9 15:34 EDT 2021. Contains 343742 sequences. (Running on oeis4.)