The OEIS is supported by the many generous donors to the OEIS Foundation.
Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #16 Apr 07 2024 09:09:39
%S 30,42,60,66,78,84,90,102,114,120,126,132,138,150,156,168,174,180,186,
%T 198,204,210,222,228,234,240,246,252,258,264,270,276,282,294,300,306,
%U 312,318,330,336,342,348,354,360,366,372,378,390,396,402,408,414,420
%N Integers k such that 3*phi(k) < k.
%C If k is present so are all m*k, m>1.
%C The smallest odd number in this sequence is 111546435 = 3*5*7*11*...*23. - _T. D. Noe_, Jan 15 2004
%H Robert Israel, <a href="/A091454/b091454.txt">Table of n, a(n) for n = 1..10000</a>
%p filter:= n -> 3*numtheory:-phi(n) < n:
%p select(filter, [$1..10000]); # _Robert Israel_, Jan 13 2020
%t Select[ Range[437], 3EulerPhi[ # ] < # & ]
%o (Magma) [k:k in [1..500]|3*EulerPhi(k) lt k]; // _Marius A. Burtea_, Jan 13 2020
%o (PARI) is(n) = 3*eulerphi(n) < n; \\ _Amiram Eldar_, Apr 07 2024
%Y Cf. A000010 (phi), A054741, A066765, A091456.
%K nonn
%O 1,1
%A _Robert G. Wilson v_, Jan 10 2004