A066449 Binomial(n, phi(n)), where phi(n) is the Euler totient function.

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

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 A358170

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