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A071416
a(n) = gcd(n, binomial(2*n, n)).
4
1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 4, 1, 2, 15, 2, 1, 6, 1, 20, 3, 2, 1, 12, 1, 2, 1, 28, 1, 2, 1, 2, 3, 2, 7, 4, 1, 2, 1, 20, 1, 42, 1, 4, 45, 2, 1, 12, 1, 2, 3, 4, 1, 6, 1, 8, 3, 2, 1, 12, 1, 2, 3, 2, 5, 66, 1, 4, 3, 10, 1, 36, 1, 2, 15, 4, 77, 6, 1, 20, 1, 2, 1, 28, 5, 2, 3, 88, 1, 10, 91, 4, 1, 2, 5
OFFSET
1,2
COMMENTS
a(n) = n for n in A014847. - Reinhard Zumkeller
a(n) = gcd(n, C(n)), C(n) the Catalan numbers. - Peter Luschny Oct 06 2011
LINKS
Eric Weisstein's World of Mathematics, Central Binomial Coefficient
EXAMPLE
a(10) = gcd(10, binomial(20, 10)) = gcd(10, 184756) = 2.
MATHEMATICA
Table[GCD[n, Binomial[2n, n]], {n, 100}] (* Harvey P. Dale, Nov 10 2011 *)
CROSSREFS
Sequence in context: A337395 A126083 A356158 * A053589 A055770 A225821
KEYWORD
nonn,nice
AUTHOR
Reinhard Zumkeller, May 29 2002
STATUS
approved