A294575 - OEIS

A294575

Numbers n such that 2 * A243823(n) > n.

144, 162, 174, 186, 192, 198, 200, 204, 216, 220, 222, 228, 230, 234, 238, 240, 246, 250, 252, 258, 260, 264, 266, 270, 276, 280, 282, 288, 290, 294, 300, 306, 308, 310, 312, 318, 320, 322, 324, 330, 336, 340, 342, 348, 350, 354, 360, 364, 366, 370, 372, 374

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OFFSET

1,1

COMMENTS

Consider A243823(n), which is the number of m < n that are products of at least one prime p | n and at least one prime q that does not divide n. These numbers m in the cototient of n do not divide a power of n. This sequence lists numbers n where such numbers m are predominant.

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000

EXAMPLE

A272619(10) = (6), A243823(10) = 1, so 10 is not in the sequence. A243823(144) = 74, which is greater than half of all numbers less than or equal to 144, thus 144 is the first term.

MATHEMATICA

Select[Range[10^3], Function[n, 2 (n - (Count[Range@ n, _?(PowerMod[n, Floor@ Log2@ n, #] == 0 &)] + EulerPhi[n] - 1)) > n]]

CROSSREFS

Cf. A243823, A272619, A294576.

Sequence in context: A173065 A044868 A162532 * A205190 A085426 A034289

Adjacent sequences: A294572 A294573 A294574 * A294576 A294577 A294578

KEYWORD

nonn

AUTHOR

Michael De Vlieger, Nov 17 2017

STATUS

approved