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A131644
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a(n) = 2^(a(n-1)) mod n.
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2
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0, 1, 2, 0, 1, 2, 4, 0, 1, 2, 4, 4, 3, 8, 1, 2, 4, 16, 5, 12, 1, 2, 4, 16, 11, 20, 4, 16, 25, 2, 4, 16, 31, 26, 4, 16, 9, 18, 25, 32, 37, 2, 4, 16, 16, 32, 42, 16, 23, 8, 1, 2, 4, 16, 31, 16, 43, 56, 15, 8, 12, 4, 16, 0, 1, 2, 4, 16, 55, 58, 29, 32, 32, 44, 16, 24, 71, 20, 9, 32, 49, 20, 37
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| All positive integers seem to occur somewhere in this sequence (a proof would be nice!).
The first occurrence of 6 is a(59474). The first occurrence of 33 is a(2514233).
a(A192362(n)) = n and a(m) <> n for m < A192362(n). [Reinhard Zumkeller, Jun 30 2011]
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
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FORMULA
| a(n) = 2^(a(n-1)) mod n, a(1) = 0
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EXAMPLE
| a(11) = 4, so a(12) = 2^a(11) mod 12 = 16 mod 12 = 4.
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MATHEMATICA
| Transpose[NestList[{Mod[2^First[#], Last[#]+1], Last[#]+1}&, {0, 1}, 95]][[1]] (* From Harvey P. Dale, Apr 17 2011 *)
Join[{s=0}, Table[s = PowerMod[2, s, n], {n, 2, 100}]] (* T. D. Noe, Apr 17 2011 *)
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CROSSREFS
| Sequence in context: A115218 A023858 A011118 * A115346 A140531 A117316
Adjacent sequences: A131641 A131642 A131643 * A131645 A131646 A131647
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KEYWORD
| easy,nonn,nice
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AUTHOR
| Jon Ayres (jonathan.ayres(AT)ntlworld.com), Sep 08 2007
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