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A091454 Integers n such that 3*phi(n) < n. 2
30, 42, 60, 66, 78, 84, 90, 102, 114, 120, 126, 132, 138, 150, 156, 168, 174, 180, 186, 198, 204, 210, 222, 228, 234, 240, 246, 252, 258, 264, 270, 276, 282, 294, 300, 306, 312, 318, 330, 336, 342, 348, 354, 360, 366, 372, 378, 390, 396, 402, 408, 414, 420 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If n is present so are all k*n, k>1.

The smallest odd number in this sequence is 111546435 = 3*5*7*11*...*23. - T. D. Noe, Jan 15 2004

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

filter:= n -> 3*numtheory:-phi(n) < n:

select(filter, [$1..10000]); # Robert Israel, Jan 13 2020

MATHEMATICA

Select[ Range[437], 3EulerPhi[ # ] < # & ]

PROG

(MAGMA) [k:k in [1..500]|3*EulerPhi(k) lt k]; // Marius A. Burtea, Jan 13 2020

CROSSREFS

Cf. A000010, A054741, A091456.

Sequence in context: A033992 A214195 A308127 * A175727 A296717 A302753

Adjacent sequences:  A091451 A091452 A091453 * A091455 A091456 A091457

KEYWORD

nonn,changed

AUTHOR

Robert G. Wilson v, Jan 10 2004

STATUS

approved

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Last modified January 20 14:02 EST 2020. Contains 331094 sequences. (Running on oeis4.)