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

Author

Joseph L. Pe, Dec 28 2001

Keywords

• easy
• nonn

Comments

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

Examples

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

Links

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

Crossrefs

Cf. A000010, A051953, A066090, A064366.

Programs

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 *)

PARI

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

Extensions

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