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A340674
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Numbers of the form s^(2^e), where s is a squarefree number, and e >= 1.
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5
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4, 9, 16, 25, 36, 49, 81, 100, 121, 169, 196, 225, 256, 289, 361, 441, 484, 529, 625, 676, 841, 900, 961, 1089, 1156, 1225, 1296, 1369, 1444, 1521, 1681, 1764, 1849, 2116, 2209, 2401, 2601, 2809, 3025, 3249, 3364, 3481, 3721, 3844, 4225, 4356, 4489, 4761, 4900
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OFFSET
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1,1
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LINKS
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FORMULA
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Sum_{n>=1} 1/a(n) = Sum_{k>=1} (zeta(2^k)/zeta(2^(k+1))-1) = 0.6018231854... - Amiram Eldar, Feb 08 2021
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MATHEMATICA
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Select[Range[10^4], Length[(u = Union[FactorInteger[#][[;; , 2]]])] == 1 && u[[1]] > 1 && u[[1]] == 2^IntegerExponent[u[[1]], 2] &] (* Amiram Eldar, Feb 08 2021 *)
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PROG
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(PARI)
A209229(n) = (n && !bitand(n, n-1));
isA340674(n) = { my(b, e); (((e=ispower(n, , &b))>0)&&issquarefree(b)&&A209229(e)); };
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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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