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Search: id:A131461
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| A131461 |
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Residues of 3^(2^p(n)-2) for Mersenne numbers with prime indices. |
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+0
6
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| 0, 1, 1, 1, 1013, 1, 1, 1, 5884965, 65165529, 1, 103888408793, 474639880182, 4112907695371, 72685811469476, 5155089749987738, 440411515280180314, 1, 95591506202441271281, 69291880649932219827
(list; graph; listen)
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OFFSET
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1,5
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COMMENT
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M_p is prime iff 3^(M_p-1) is congruent to 1 mod M_p. Thus M_7 = 127 is prime because 3^126 mod 127 = 1 while M_11 = 2047 is composite because 3^2046 mod 2047 <> 1.
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LINKS
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Dennis Martin, Table of n, a(n) for n = 1..100
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FORMULA
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a(n) = 3^(2^p(n)-2) mod 2^p(n)-1
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EXAMPLE
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a(5) = 3^(2^11-2) mod 2^11-1 = 3^2046 mod 2047 = 1013
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CROSSREFS
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Cf. A095847, A001348, A131458, A131459, A131460, A131462, A131463.
Sequence in context: A022054 A107518 A073144 this_sequence A069489 A126239 A120214
Adjacent sequences: A131458 A131459 A131460 this_sequence A131462 A131463 A131464
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KEYWORD
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nonn
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AUTHOR
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Dennis Martin (dennis.martin(AT)dptechnology.com), Jul 20 2007
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