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A285804
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Composite numbers of the form 12*k+5 or 12*k+7 for some k.
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0
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55, 65, 77, 91, 115, 125, 161, 175, 185, 187, 209, 221, 235, 245, 247, 259, 295, 305, 319, 329, 341, 343, 355, 365, 377, 391, 403, 413, 415, 425, 427, 437, 451, 473, 475, 485, 497, 511, 533, 535, 545, 559, 581, 583, 595, 605, 629, 655, 665
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OFFSET
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1,1
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COMMENTS
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Conjecture: Let r(n) = (a(n)-1)/(a(n)+1)) if a(n) mod 4 = 1, (a(n)+1)/(a(n)-1)) otherwise; then Product_{n>=1} r(n) = (28/27) * (32/33) * (38/39) * (46/45) * ... = 1.
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LINKS
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MAPLE
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remove(isprime, [seq(seq(12*k+j, j=[5, 7]), k=1..100)]); # Robert Israel, Apr 28 2017
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PROG
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(PARI) {
for(n=0, 100,
n12=12*n; n5=n12+5; n7=n12+7;
if(!isprime(n5), print1(n5", "));
if(!isprime(n7), print1(n7", "))
)
}
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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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