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A071639
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Numbers k such that core(k) = b(k,1)*b(k,0) where b(k,1) is the number of 1's in binary representation of k, b(k,0) the number of 0's and core(k) the squarefree part of k.
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1
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24, 3500, 6048, 52855, 56320, 67270, 71874, 80920, 85536, 95830, 105600, 112000, 117670, 131625, 142373, 155925, 250173, 262392, 280800, 350142, 360672, 673036, 965419, 984256, 1041859, 1078110, 1144440, 1166990, 1283040, 1331000, 1355310, 1454750, 1480160, 1691360
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OFFSET
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1,1
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LINKS
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Amiram Eldar, Table of n, a(n) for n = 1..1000
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MATHEMATICA
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core[n_] := Times @@ (First[#]^Mod[Last[#], 2]& /@ FactorInteger[n]); b[n_] := Times @@ DigitCount[n, 2, {0, 1}]; Select[Range[10^5], core[#] == b[#] &] (* Amiram Eldar, Sep 03 2020 *)
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PROG
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(PARI) for(s=1, 500000, b=binary(s); l=length(b); if(sum(i=1, l, if(component(b, i)-1, 0, 1))*sum(i=1, l, if(component(b, i), 0, 1))==core(s), print1(s, ", ")))
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CROSSREFS
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Cf. A007913, A071295.
Sequence in context: A349115 A159681 A275569 * A061530 A275637 A223123
Adjacent sequences: A071636 A071637 A071638 * A071640 A071641 A071642
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KEYWORD
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easy,nonn,base
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AUTHOR
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Benoit Cloitre, Jun 22 2002
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EXTENSIONS
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More terms from Amiram Eldar, Sep 03 2020
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STATUS
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approved
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