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A066449 Binomial(n, phi(n)), where phi(n) is the Euler totient function. 4
1, 2, 3, 6, 5, 15, 7, 70, 84, 210, 11, 495, 13, 3003, 6435, 12870, 17, 18564, 19, 125970, 293930, 646646, 23, 735471, 53130, 9657700, 4686825, 30421755, 29, 5852925, 31, 601080390, 573166440, 2203961430, 417225900, 1251677700, 37, 33578000610 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This is also binomial(n, cototient(n)). - Franklin T. Adams-Watters, Jul 13 2014

LINKS

Harry J. Smith, Table of n, a(n) for n=1..300

EXAMPLE

a(6) = binomial(6, phi(6)) = binomial(6, 2) = 6!/(2!*4!) = 15.

MAPLE

seq(binomial(n, numtheory:-phi(n)), n=1..100); # Robert Israel, Jul 13 2014

MATHEMATICA

Map[Binomial[#, EulerPhi[#]] &, Range[80]] (* Carl Najafi, Aug 30 2011 *)

PROG

(PARI) { for (n=1, 300, a=binomial(n, eulerphi(n)); write("b066449.txt", n, " ", a) ) } \\ Harry J. Smith, Feb 15 2010

CROSSREFS

Cf. A000010, A051953, A066090, A064366.

Sequence in context: A100211 A071257 A067392 * A276942 A255483 A098012

Adjacent sequences:  A066446 A066447 A066448 * A066450 A066451 A066452

KEYWORD

easy,nonn

AUTHOR

Joseph L. Pe, Dec 28 2001

EXTENSIONS

a(16) - a(38) from Harry J. Smith, Feb 15 2010

STATUS

approved

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Last modified October 16 05:32 EDT 2019. Contains 328044 sequences. (Running on oeis4.)