1,2

a(6) = C(6,EulerPhi(6)) = C(6,2) = 6!/(2!4!) = 15.

Cf. A000010.

Sequence in context: A100211 A071257 A067392 this_sequence A098012 A066117 A124655

Adjacent sequences: A066446 A066447 A066448 this_sequence A066450 A066451 A066452

easy,nonn

Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Dec 28 2001