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A047239
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Numbers that are congruent to {1, 2} mod 6.
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0
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1, 2, 7, 8, 13, 14, 19, 20, 25, 26, 31, 32, 37, 38, 43, 44, 49, 50, 55, 56, 61, 62, 67, 68, 73, 74, 79, 80, 85, 86, 91, 92, 97, 98, 103, 104, 109, 110, 115, 116, 121, 122, 127, 128, 133, 134, 139, 140, 145, 146, 151
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (1,1,-1).
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FORMULA
| a(n)=3*(n-1)-(-1)^n [From Rolf Pleisch (r_pleisch(AT)gmx.ch), Aug 04 2009]
a(n)=6*n-a(n-1)-9 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 05 2010]
G.f. x*(1+x+4*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Oct 08 2011
a(1)=1, a(2)=2, a(3)=7, a(n)=a(n-1)+a(n-2)-a(n-3) [From Harvey P. Dale, Nov 23 2011]
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EXAMPLE
| For n=2, a(2)=6*2-1-9=2; n=3, a(3)=6*3-2-9=7; n=4, a(4)=6*4-7-9=8 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 05 2010]
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MATHEMATICA
| Select[Range[200], MemberQ[{1, 2}, Mod[#, 6]]&] (* or *) LinearRecurrence[ {1, 1, -1}, {1, 2, 7}, 80] (* From Harvey P. Dale, Nov 23 2011 *)
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CROSSREFS
| Sequence in context: A070044 A129850 A037073 * A032927 A004717 A063531
Adjacent sequences: A047236 A047237 A047238 * A047240 A047241 A047242
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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