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A090333
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Nonprimes with no divisors >1 that are prefixes of other divisors in binary representation.
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2
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1, 9, 25, 33, 35, 49, 65, 69, 77, 91, 121, 125, 129, 133, 141, 143, 145, 155, 161, 169, 209, 247, 259, 265, 267, 287, 289, 295, 299, 301, 305, 319, 323, 329, 341, 343, 361, 371, 377, 391, 395, 403, 407, 437, 451, 473, 481, 485, 493, 505, 515, 519, 527, 529, 533
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OFFSET
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1,2
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COMMENTS
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LINKS
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MAPLE
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filter:= proc(n) local d, i, j;
if isprime(n) then return false fi;
d:= numtheory:-divisors(n);
for i in d do
for j from 1 to ilog2(i)-1 do
if member(floor(i/2^j), d) then return false fi
od od;
true
end proc:
select(filter, [seq(i, i=1..1000, 2)]); # Robert Israel, Jul 08 2020
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MATHEMATICA
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filterQ[n_] := If[PrimeQ[n], False, Catch@Module[{d = Divisors[n], j}, Do[For[j = 1, j <= Floor@Log[2, i]-1, j++, If[MemberQ[d, Floor[i/2^j]], Throw[False]]], {i, d}]; True]];
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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