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A047216
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Numbers that are congruent to {1, 2} mod 5.
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21
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1, 2, 6, 7, 11, 12, 16, 17, 21, 22, 26, 27, 31, 32, 36, 37, 41, 42, 46, 47, 51, 52, 56, 57, 61, 62, 66, 67, 71, 72, 76, 77, 81, 82, 86, 87, 91, 92, 96, 97, 101, 102, 106, 107, 111, 112, 116, 117, 121, 122, 126, 127, 131, 132, 136, 137, 141, 142, 146, 147
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OFFSET
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1,2
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COMMENTS
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This sequence is related to A176059 by a(n) = sum(A176059(i), i=0..n-1) - A176059(n).
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LINKS
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Table of n, a(n) for n=1..60.
Index to sequences with linear recurrences with constant coefficients, signature (1,1,-1).
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FORMULA
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a(n) = 5*n-a(n-1)-7 with n>1, a(1)=1. - Vincenzo Librandi, Aug 05 2010
G.f. x*(1+x+3*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Oct 08 2011
a(n) = (10*n-3*(-1)^n-9)/4. - Bruno Berselli, Mar 10 2012
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MATHEMATICA
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Select[Range[0, 200], MemberQ[{1, 2}, Mod[#, 5]] &] (* From Vladimir Joseph Stephan Orlovsky, Feb 12 2012 *)
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PROG
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(PARI) a(n)=(n-1)\2*5+2-n%2 \\ Charles R Greathouse IV, Dec 22 2011
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CROSSREFS
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Cf. A047209, A047211, A047212, A176059.
Sequence in context: A029507 A047552 A221847 * A039568 A032926 A214991
Adjacent sequences: A047213 A047214 A047215 * A047217 A047218 A047219
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KEYWORD
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nonn,easy,changed
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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