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%I #30 Dec 12 2023 08:28:59
%S 1,2,8,24,72,240,960,2880,15360,69120,165888,912384,3041280,9123840,
%T 34062336,127733760,479001600,1596672000,6386688000,22992076800,
%U 102187008000,429185433600,1755758592000,6730407936000,28267713331200
%N a(n) = phi(binomial(2n, n)).
%H Harry J. Smith, <a href="/A066973/b066973.txt">Table of n, a(n) for n = 1..200</a>
%F a(n) = A000010(A000984(n)).
%p with(numtheory):with(combinat):a:=n->phi(binomial(2*n,n)): seq(a(n), n=1..25); # _Zerinvary Lajos_, Oct 05 2007
%t f[n_] := EulerPhi[Binomial[2n,n]]; Table[f[n], {n,100}] (* _Enrique Pérez Herrero_, Jan 31 2012 *)
%o (SageMath) [euler_phi(binomial(2*n,n))for n in range(1,26)] # _Zerinvary Lajos_, Jun 06 2009
%o (PARI) a(n) = eulerphi(binomial(2*n, n)); \\ _Harry J. Smith_, Apr 12 2010
%K nonn
%O 1,2
%A _Benoit Cloitre_, Jan 26 2002
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