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 A181861 a(n) = gcd(n^2, n!/floor(n/2)!^2). 3
 1, 1, 2, 3, 2, 5, 4, 7, 2, 9, 4, 11, 12, 13, 4, 45, 2, 17, 4, 19, 4, 21, 4, 23, 4, 25, 4, 27, 8, 29, 180, 31, 2, 99, 4, 175, 12, 37, 4, 117, 20, 41, 12, 43, 8, 675, 4, 47, 36, 49, 4, 153, 8, 53, 4, 55, 56, 57, 4, 59, 16 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Marius A. Burtea, Table of n, a(n) for n = 0..1000 FORMULA a(n) = gcd(A000290(n), A056040(n)). MAPLE A181861 := n -> igcd(n^2, n!/iquo(n, 2)!^2); MATHEMATICA sf[n_] := n!/Quotient[n, 2]!^2; Table[GCD[n^2, sf[n]], {n, 0, 60}] (* Jean-François Alcover, Jun 28 2013 *) PROG (PARI) a(n)=gcd(n!/(n\2)!^2, n^2) \\ Charles R Greathouse IV, Feb 01 2013 (Magma) [Gcd(n^2, Floor(Factorial(n)/(Factorial(Floor(n/2))^2))):n in [0..60]]; // Marius A. Burtea, Aug 03 2019 CROSSREFS Cf. A170826, A181860, A056040, A000290. Sequence in context: A238729 A182816 A195637 * A365099 A342694 A212831 Adjacent sequences: A181858 A181859 A181860 * A181862 A181863 A181864 KEYWORD nonn AUTHOR Peter Luschny, Nov 21 2010 STATUS approved

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Last modified September 24 22:14 EDT 2023. Contains 365582 sequences. (Running on oeis4.)