A066973 a(n) = phi(binomial(2n, n)).

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

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

(SageMath) [euler_phi(binomial(2*n, n))for n in range(1, 26)] # Zerinvary Lajos, Jun 06 2009
(PARI) a(n) = eulerphi(binomial(2*n, n)); \\ Harry J. Smith, Apr 12 2010

Crossrefs

Sequence in context: A363602 A290904 A231200 * A130495 A026070 A093833

Adjacent sequences: A066970 A066971 A066972 * A066974 A066975 A066976

Keyword

nonn

Author

Benoit Cloitre, Jan 26 2002

Status

approved