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A227854
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Loeschian 3-almost primes: numbers with exactly three prime factors (with multiplicity) and of the form x^2 + x*y + y^2.
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1
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12, 27, 28, 52, 63, 75, 76, 117, 124, 147, 148, 171, 172, 175, 244, 268, 273, 279, 292, 316, 325, 333, 343, 363, 387, 388, 399, 412, 436, 475, 507, 508, 549, 556, 603, 604, 628, 637, 651, 652, 657, 711, 724, 741, 772, 775, 777, 796, 844, 847, 867, 873, 892
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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EXAMPLE
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a(1) = 12 = 2^2 * 3 = 2^2 + 2*2 + 2^2 (x = y = 2).
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PROG
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(PARI) list(lim)=my(v=List(), y, t); for(x=1, sqrtint(lim\3), my(y=x, t); while((t=x^2+x*y+y^2)<=lim, if(bigomega(t)==3, listput(v, t)); y++)); Set(v) \\ Charles R Greathouse IV, Feb 05 2017
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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