A066765 Numbers k such that phi(k) < k/5.

30030, 39270, 43890, 46410, 51870, 53130, 60060, 78540, 87780, 90090, 92820, 103740, 106260, 117810, 120120, 131670, 139230, 150150, 155610, 157080, 159390, 175560, 180180, 185640, 196350, 207480, 210210, 212520, 219450, 232050, 235620

Offset: 1

Author

Jason Earls, Jan 17 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)

Crossrefs

Cf. A000010 (phi), A091454.

Programs

Mathematica

Select[Range[250000], EulerPhi[#] < #/5 &] (* Amiram Eldar, Apr 07 2024 *)

PARI

for(n=1,10^8, if(eulerphi(n)
				

PARI

{ n=0; for (m=1, 10^10, if (eulerphi(m) < m/5, write("b066765.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Mar 24 2010

PARI

list(lim)=my(v=List()); forfactored(n=30030,lim\1, if(5*eulerphi(n)Charles R Greathouse IV, Jan 16 2025

Formula

a(n) ~ kn for some constant k. k seems to be near 6500. - Charles R Greathouse IV, Jan 16 2025