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A082295 Numbers having more than two square divisors > 1. 3
36, 64, 72, 100, 108, 128, 144, 180, 192, 196, 200, 216, 225, 252, 256, 288, 300, 320, 324, 360, 384, 392, 396, 400, 432, 441, 448, 450, 468, 484, 500, 504, 512, 540, 576, 588, 600, 612, 640, 648, 675, 676, 684, 700, 704, 720, 729, 756, 768, 784, 792, 800 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
If n is in the sequence, so is m*n. - Charles R Greathouse IV, Oct 16 2015
The asymptotic density of this sequence is 1 - (6/Pi^2) * (1 + Sum_{p prime} (1/p^2 + 1/(p^3*(p+1)) + 1/(p^4*(p+1)))) = 0.07033321843992718294... . - Amiram Eldar, Sep 25 2022
LINKS
FORMULA
A046951(a(n)) > 3.
a(n) < 17n for n > 25. - Charles R Greathouse IV, Oct 16 2015
EXAMPLE
n=200 has 4 square divisors: 1, 4, 25 and 100, therefore 200 is a term.
MATHEMATICA
Select[Range[1000], Length[Rest[Select[ Divisors[#], IntegerQ[ Sqrt[ #]]&]]]> 2&] (* Harvey P. Dale, Jan 08 2014 *)
PROG
(PARI) is(n)=my(f=vecsort(factor(n)[, 2], , 4)); #f && (f[1]>5 || (#f>1 && f[2]>1)) \\ Charles R Greathouse IV, Oct 16 2015
CROSSREFS
Sequence in context: A043242 A044022 A337862 * A343293 A326666 A272190
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 08 2003
STATUS
approved

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Last modified July 21 02:16 EDT 2024. Contains 374462 sequences. (Running on oeis4.)