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 A066973 a(n) = phi(binomial(2n, n)). 4
 1, 2, 8, 24, 72, 240, 960, 2880, 15360, 69120, 165888, 912384, 3041280, 9123840, 34062336, 127733760, 479001600, 1596672000, 6386688000, 22992076800, 102187008000, 429185433600, 1755758592000, 6730407936000, 28267713331200 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Harry J. Smith, Table of n, a(n) for n = 1..200 FORMULA a(n) = A000010(A000984(n)). MAPLE with(numtheory):with(combinat):a:=n->phi(binomial(2*n, n)): seq(a(n), n=1..25); # Zerinvary Lajos, Oct 05 2007 MATHEMATICA f[n_] := EulerPhi[Binomial[2n, n]]; Table[f[n], {n, 100}] (* Enrique Pérez Herrero, Jan 31 2012 *) PROG (sage) [euler_phi(binomial(2*n, n))for n in range(1, 26)] # Zerinvary Lajos, Jun 06 2009 (PARI) { for (n=1, 200, write("b066973.txt", n, " ", eulerphi(binomial(2*n, n))) ) } \\ Harry J. Smith, Apr 12 2010 CROSSREFS Sequence in context: A131569 A290904 A231200 * A130495 A026070 A093833 Adjacent sequences:  A066970 A066971 A066972 * A066974 A066975 A066976 KEYWORD nonn AUTHOR Benoit Cloitre, Jan 26 2002 STATUS approved

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Last modified June 24 00:14 EDT 2021. Contains 345403 sequences. (Running on oeis4.)