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A047280 Numbers that are congruent to {3, 6} mod 7. 7
3, 6, 10, 13, 17, 20, 24, 27, 31, 34, 38, 41, 45, 48, 52, 55, 59, 62, 66, 69, 73, 76, 80, 83, 87, 90, 94, 97, 101, 104, 108, 111, 115, 118, 122, 125, 129, 132, 136, 139, 143, 146, 150, 153, 157, 160, 164, 167, 171, 174, 178, 181, 185, 188, 192, 195, 199, 202 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..58.

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

a(n) = 7*n-a(n-1)-5 with n>1, a(1)=3. [Vincenzo Librandi, Aug 05 2010]

G.f.: x*(3+3*x+x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Oct 25 2011

a(n) = 3*n + ceiling(n/2) - 1. - Arkadiusz Wesolowski, Sep 20 2012

a(n) = 4n - 1 - floor(n/2). - Wesley Ivan Hurt, Oct 16 2013

MAPLE

A047280:=n->4*n-1-floor(n/2); seq(A047280(k), k=1..100); # Wesley Ivan Hurt, Oct 16 2013

MATHEMATICA

Flatten[#+{3, 6}&/@(7Range[0, 30])]  (* Harvey P. Dale, Jan 11 2011 *)

CROSSREFS

Sequence in context: A145383 A258834 A194028 * A310054 A310055 A310056

Adjacent sequences:  A047277 A047278 A047279 * A047281 A047282 A047283

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified August 18 13:25 EDT 2019. Contains 326100 sequences. (Running on oeis4.)