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A340585
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Noncube perfect powers.
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2
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4, 9, 16, 25, 32, 36, 49, 81, 100, 121, 128, 144, 169, 196, 225, 243, 256, 289, 324, 361, 400, 441, 484, 529, 576, 625, 676, 784, 841, 900, 961, 1024, 1089, 1156, 1225, 1296, 1369, 1444, 1521, 1600, 1681, 1764, 1849, 1936, 2025, 2048, 2116, 2187, 2209, 2304, 2401, 2500
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OFFSET
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1,1
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COMMENTS
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This was the original definition of A239870. However, the true definition of that sequence seems to be slightly different.
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LINKS
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FORMULA
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Sum_{n>=1} 1/a(n) = 1 - zeta(3) + Sum_{k>=2} mu(k)*(1-zeta(k)) = 1 - A002117 + A072102 = 0.6724074652... - Amiram Eldar, Jan 12 2021
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MAPLE
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filter:= proc(n) local g;
g:= igcd(op(ifactors(n)[2][.., 2]));
g > 1 and (g mod 3 <> 0)
end proc:
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MATHEMATICA
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Select[Range[2, 2500], (g = GCD @@ FactorInteger[#][[;; , 2]]) > 1 && !Divisible[g, 3] &] (* Amiram Eldar, Jan 12 2021 *)
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PROG
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(PARI) for(n=2, 2500, if( ispower(n) % 3, print1(n, ", ")))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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