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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 xrange(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 May 20 03:10 EDT 2019. Contains 323412 sequences. (Running on oeis4.)