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A045897
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Has both a primitive and imprimitive representation as x^2 + xy + y^2.
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6
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49, 147, 169, 343, 361, 507, 637, 931, 961, 1029, 1083, 1183, 1369, 1519, 1813, 1849, 1911, 2107, 2197, 2401, 2527, 2793, 2883, 2989, 3211, 3283, 3549, 3577, 3721, 3871, 4107, 4459, 4489, 4557, 4693, 4753, 5047, 5239, 5329, 5341, 5439, 5547, 6223, 6241
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OFFSET
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1,1
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LINKS
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EXAMPLE
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49 = 7^2 = 5^2 + 5*3 + 3^2.
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PROG
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(PARI) is(n)=my(f=factor(n), t); for(i=1, #f~, if(f[i, 1]%3!=1 && (f[i, 1]!=3 || f[i, 2]>1), return(0)); if(f[i, 1]%3<2 && f[i, 2]>1, t=1); if(f[i, 1]%3==2, if(f[i, 2]%2, return(0), t=1))); t \\ Charles R Greathouse IV, Nov 04 2015
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CROSSREFS
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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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