A066973 - OEIS

%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