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A176256
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Numbers of the form 4k+1 with least prime divisor of the form 4m-1.
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7
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9, 21, 33, 45, 49, 57, 69, 77, 81, 93, 105, 117, 121, 129, 133, 141, 153, 161, 165, 177, 189, 201, 209, 213, 217, 225, 237, 249, 253, 261, 273, 285, 297, 301, 309, 321, 329, 333, 341, 345, 357, 361, 369, 381, 393, 405, 413, 417, 429, 437, 441, 453, 465, 469
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OFFSET
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1,1
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COMMENTS
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By definition, all terms are composite numbers.
Cannot be the hypotenuse of a primitive Pythagorean triangle. - Robert G. Wilson v, Mar 16 2014
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LINKS
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MATHEMATICA
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fQ[n_] := Mod[ n, 4] == 1 && Mod[ FactorInteger[n][[1, 1]], 4] == 3; Select[Range@470, fQ] (* Robert G. Wilson v, Apr 08 2014 *)
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PROG
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(PARI) isok(n) = ((n % 4) == 1) && (f = factor(n)) && ((f[1, 1] % 4) == 3); \\ Michel Marcus, Mar 16 2014
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CROSSREFS
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Complement of A020882 in 1 == Mod 4.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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