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 A057815 a(n) = GCD(n, C(n, floor(n/2))). 1
 1, 2, 3, 2, 5, 2, 7, 2, 9, 2, 11, 12, 13, 2, 15, 2, 17, 2, 19, 4, 21, 2, 23, 4, 25, 2, 27, 4, 29, 30, 31, 2, 33, 2, 35, 12, 37, 2, 39, 20, 41, 6, 43, 4, 45, 2, 47, 12, 49, 2, 51, 4, 53, 2, 55, 56, 57, 2, 59, 4, 61, 2, 63, 2, 65, 6, 67, 4, 69, 14, 71, 4, 73, 2, 75, 4, 77, 2, 79, 20, 81, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE a(2k+1)=2k+1. For even n, a(n) is an even divisor of n: a(2k)=2,2,2,2,12,2,2,2,4,... as in A058005. MAPLE swing := n -> n!/iquo(n, 2)!^2: seq(igcd(n, swing(n)), n=1..82); # Peter Luschny, May 17 2013 CROSSREFS Cf. A001405, A049077. Sequence in context: A141310 A007389 A007388 * A007387 A105222 A280503 Adjacent sequences:  A057812 A057813 A057814 * A057816 A057817 A057818 KEYWORD nonn AUTHOR Labos Elemer, Nov 13 2000 EXTENSIONS Offset changed to 1. Peter Luschny, May 17 2013 STATUS approved

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Last modified January 17 23:15 EST 2019. Contains 319251 sequences. (Running on oeis4.)