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A047288 Numbers that are congruent to {4, 6} mod 7. 5
4, 6, 11, 13, 18, 20, 25, 27, 32, 34, 39, 41, 46, 48, 53, 55, 60, 62, 67, 69, 74, 76, 81, 83, 88, 90, 95, 97, 102, 104, 109, 111, 116, 118, 123, 125, 130, 132, 137, 139, 144, 146, 151, 153, 158, 160, 165, 167, 172 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
a(n) = 7*n - a(n-1) - 4 with n > 1, a(1)=4. - Vincenzo Librandi, Aug 05 2010
From Colin Barker, Mar 13 2012: (Start)
a(n) = a(n-1) + a(n-2) - a(n-3).
G.f.: x*(4 + 2*x + x^2)/((1-x)^2*(1+x)). (End)
a(n) = (-1 - 3*(-1)^n + 14*n)/4. - Colin Barker, May 14 2012
a(n) = floor(7*n/2) - (-1)^n. - Wesley Ivan Hurt, Sep 12 2017
E.g.f.: 1 + ((14*x - 1)*exp(x) - 3*exp(-x))/4. - David Lovler, Sep 15 2022
MATHEMATICA
LinearRecurrence[{1, 1, -1}, {4, 6, 11}, 50] (* Harvey P. Dale, Jan 18 2013 *)
PROG
(PARI) a(n) = (-1 - 3*(-1)^n + 14*n)/4 \\ David Lovler, Sep 15 2022
CROSSREFS
Sequence in context: A250125 A190489 A094226 * A287565 A163417 A247336
KEYWORD
nonn,easy
AUTHOR
STATUS
approved

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Last modified March 28 10:55 EDT 2024. Contains 371241 sequences. (Running on oeis4.)