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A253906
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Numbers n such that n^2 + 3 and n^3 + 3 are semiprime.
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3
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1, 6, 20, 34, 40, 44, 46, 56, 102, 116, 120, 170, 174, 196, 200, 204, 220, 226, 232, 234, 252, 260, 262, 294, 296, 320, 334, 336, 344, 346, 358, 360, 382, 386, 392, 412, 426, 464, 476, 482, 490, 494, 514, 520, 526, 536, 556, 564, 582, 586, 592, 646, 658, 716
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OFFSET
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1,2
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COMMENTS
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All terms in this sequence, except a(1), are even.
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LINKS
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EXAMPLE
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a(2) = 6;
6^2 + 3 = 39 = 3 * 13;
6^3 + 3 = 219 = 3 * 73;
Both are semiprime.
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MATHEMATICA
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Select[Range[10^3], k = 3; PrimeOmega[(#^2 + k)] == 2 && PrimeOmega[(#^3 + k)] == 2 &]
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PROG
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(PARI)
issemiprime(q) = q>0 && bigomega(q)==2
select(n->issemiprime(n^2+3)&&issemiprime(n^3+3), vector(2000, n, n)) \\ Colin Barker, Jan 28 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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STATUS
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approved
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