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A047320 Numbers that are congruent to {0, 5, 6} mod 7. 1
0, 5, 6, 7, 12, 13, 14, 19, 20, 21, 26, 27, 28, 33, 34, 35, 40, 41, 42, 47, 48, 49, 54, 55, 56, 61, 62, 63, 68, 69, 70, 75, 76, 77, 82, 83, 84, 89, 90, 91, 96, 97, 98, 103, 104, 105, 110, 111, 112, 117, 118, 119, 124, 125, 126, 131, 132, 133, 138, 139, 140 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..61.

Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).

FORMULA

G.f.: x^2*(5+x+x^2) / ((1+x+x^2)*(x-1)^2). - R. J. Mathar, Dec 03 2011

From Wesley Ivan Hurt, Jun 07 2016: (Start)

a(n) = a(n-1) + a(n-3) - a(n-4) for n>4.

a(n) = (21*n-9-8*sqrt(3)*sin(2*n*Pi/3))/9.

a(3k) = 7k-1, a(3k-1) = 7k-2, a(3k-2) = 7k-7. (End)

MAPLE

A047320:=n->(21*n-9-8*sqrt(3)*sin(2*n*Pi/3))/9: seq(A047320(n), n=1..100); # Wesley Ivan Hurt, Jun 07 2016

MATHEMATICA

Select[Range[0, 200], MemberQ[{0, 5, 6}, Mod[#, 7]]&] (* Harvey P. Dale, May 25 2012 *)

PROG

(MAGMA) [n : n in [0..150] | n mod 7 in [0, 5, 6]]; // Wesley Ivan Hurt, Jun 07 2016

CROSSREFS

Sequence in context: A037360 A120521 A022566 * A327301 A247522 A011761

Adjacent sequences:  A047317 A047318 A047319 * A047321 A047322 A047323

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified September 23 02:41 EDT 2021. Contains 347609 sequences. (Running on oeis4.)