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Search: id:A132435
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| A132435 |
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Composite integers n with two prime factors nearly equidistant from the integer part of the square root of n. |
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+0
2
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| 4, 6, 9, 10, 14, 22, 25, 35, 49, 55, 65, 77, 85, 91, 119, 121, 143, 169, 187, 209, 221, 247, 253, 289, 299, 319, 323, 361, 377, 391, 407, 437, 493, 527, 529, 551, 589, 629, 667, 697, 703, 713, 841, 851, 899, 943, 961, 989, 1073, 1081, 1147, 1189
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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An integer n is included if, for some value y >= 0: n = A007918(A000196(n) + y) * A007918(A000196(n) - y) Or: n = nextprime(sqrtint(n) + y) * nextprime(sqrtint(n) - y) Where "nextprime(x)" is the smallest prime number >= to x and "sqrtint(z)" is the integer part of the square root of z.
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EXAMPLE
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25 = nextprime(5 + 0) * nextprime(5 - 0) = 5 * 5 = 25
35 = nextprime(5 + 1) * nextprime(5 - 1) = 7 * 5 = 35
119 = nextprime(10 + 4) * nextprime(10 - 4) = 17 * 7 = 119
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PROGRAM
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(PARI) bal(x, y) = nextprime(sqrtint(x)+y) * nextprime(sqrtint(x)-y); findbal(x) = local(z, y); z=sqrtint(x); while( 0<=z, y=bal(x, z); if(y==x, print1(x", "); break; ); z--; ); for (n=1, 1200, findbal(n));
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CROSSREFS
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Cf. A007918, A000196.
Sequence in context: A084759 A054395 A142863 this_sequence A108631 A099303 A005659
Adjacent sequences: A132432 A132433 A132434 this_sequence A132436 A132437 A132438
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KEYWORD
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nonn
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AUTHOR
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Andrew Plewe (aplewe(AT)sbcglobal.net), Nov 13 2007
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