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A036785
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Numbers divisible by the squares of two distinct primes.
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17
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36, 72, 100, 108, 144, 180, 196, 200, 216, 225, 252, 288, 300, 324, 360, 392, 396, 400, 432, 441, 450, 468, 484, 500, 504, 540, 576, 588, 600, 612, 648, 675, 676, 684, 700, 720, 756, 784, 792, 800, 828, 864, 882, 900, 936, 968, 972, 980, 1000, 1008, 1044
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OFFSET
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1,1
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COMMENTS
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Not squarefree, not a nontrivial prime power and not in {squarefree} times {nontrivial prime powers}.
Numbers k such that A056170(k) > 1. The asymptotic density of this sequence is 1 - (6/Pi^2) * (1 + A154945) = 0.05668359058... - Amiram Eldar, Nov 01 2020
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REFERENCES
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CRC Standard Mathematical Tables and Formulae, 30th ed., (1996) page 102-105.
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LINKS
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MATHEMATICA
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Select[Range@ 1050, And[Length@ # > 1, Total@ Boole@ Map[# > 1 &, #[[All, -1]]] > 1] &@ FactorInteger@ # &] (* Michael De Vlieger, Apr 25 2017 *)
dstdpQ[n_]:=Length[Select[Sqrt[#]&/@Divisors[n], PrimeQ]]>1; Select[ Range[ 1100], dstdpQ] (* Harvey P. Dale, Jan 15 2020 *)
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PROG
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CROSSREFS
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Equivalent sequence for 3 distinct primes: A318720.
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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More terms from Larry Reeves (larryr(AT)acm.org), Apr 03 2000
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STATUS
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approved
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