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Search: id:A155086
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| A155086 |
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Numbers a(n) such that a(n)^2 == -1 ( mod 13) . |
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+0
6
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| 5, 8, 18, 21, 31, 34, 44, 47, 57, 60, 70, 73, 83, 86, 96, 99, 109, 112, 122, 125, 135, 138, 148, 151, 161, 164, 174, 177, 187, 190, 200, 203, 213, 216, 226, 229, 239, 242, 252, 255, 265, 268, 278, 281, 291, 294, 304, 307, 317, 320, 330, 333
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Sequences b(n)^2 == -1 (mod m) exist for m in A008784; this here is m=13.
Except for the first term, a(n)=13*n-a(n-1), (with a(1)=8) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Oct 22 2009]
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FORMULA
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a(n) = a(n-1)+a(n-2)-a(n-3). G.f.: x*(5+3*x+5*x^2)/((1+x)*(x-1)^2) .
a(n) = 13*(n-1/2)/2 -7*(-1)^n/4.
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CROSSREFS
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Cf. A002144, A047221 (m=5), A155095 (m=17), A156619 (m=25), A155096 (m=29), A155097 (m=37), A155098 (m=41), A154609 (bisection)
Sequence in context: A027601 A057592 A104321 this_sequence A026595 A034453 A143157
Adjacent sequences: A155083 A155084 A155085 this_sequence A155087 A155088 A155089
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KEYWORD
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nonn,easy
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AUTHOR
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Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Jan 20 2009
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EXTENSIONS
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Algebra simplified by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 18 2009
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