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Search: id:A108868
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| A108868 |
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Numbers n such that n^5 + 3 is semiprime. |
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1
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| 1, 2, 4, 6, 11, 14, 18, 19, 24, 31, 32, 38, 40, 46, 50, 55, 59, 70, 74, 76, 84, 92, 96, 100, 115, 119, 128, 139, 148, 150, 151, 154, 155, 158, 164, 178, 184, 200, 203, 204, 206, 210, 230, 236, 238, 239, 242, 248, 256, 263, 272, 278, 284, 295, 299, 304, 306, 310
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Note that n^5 + 3 is irreducible over integers, unlike n^5 + 1 as in A104238.
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EXAMPLE
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1^5 + 3 = 4 = 2 * 2
2^5 + 3 = 35 = 5 * 7
4^5 + 3 = 1027 = 13 * 79
6^5 + 3 = 7779 = 3 * 2593
11^5 + 3 = 161054 = 2 * 80527
14^5 + 3 = 89 * 6043
100^5 + 3 = 10000000003 = 7 * 1428571429
1000^5 + 3 = 1000000000000003 = 14902357 * 67103479
1000000^5 + 3 = 1000000000000000000000000000003 = 1859827 * 537684419034673655130289.
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MAPLE
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with(numtheory): a:=proc(n) if bigomega(n^5+3)=2 then n else fi end: seq(a(n), n=1..400); (Deutsch)
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CROSSREFS
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Cf. A104238, A108814.
Sequence in context: A030783 A136969 A068059 this_sequence A138461 A103580 A094866
Adjacent sequences: A108865 A108866 A108867 this_sequence A108869 A108870 A108871
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Jul 12 2005
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Jul 16 2005
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