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A047383
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Numbers that are congruent to {1, 5} mod 7.
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2
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1, 5, 8, 12, 15, 19, 22, 26, 29, 33, 36, 40, 43, 47, 50, 54, 57, 61, 64, 68, 71, 75, 78, 82, 85, 89, 92, 96, 99, 103, 106, 110, 113, 117, 120, 124, 127, 131, 134, 138, 141, 145, 148, 152, 155, 159, 162, 166, 169
(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)=Ceiling[(7n+2)/2]
a(n)=7*n-a(n-1)-8 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 05 2010]
Contribution from Paolo P. Lava (paoloplava(AT)gmail.com), Aug 26 2010: (Start)
a(n)=(1/4)*[(-1)^n+14*n-9], with n>=1
a(n)=-2+Sum_{k=1..n}{(1/2)*[7+(-1)^k]} (End)
G.f. x*(1+4*x+2*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Oct 08 2011
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EXAMPLE
| For n=2, a(2)=7*2-1-8=5; n=3, a(3)=7*3-5-8=8; n=4, a(4)=7*4-8-8=12 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 05 2010]
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CROSSREFS
| Cf. A001106.
Sequence in context: A184915 A108173 A186276 * A133795 A190708 A145285
Adjacent sequences: A047380 A047381 A047382 * A047384 A047385 A047386
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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