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A047284 Numbers that are congruent to {2, 3, 6} mod 7. 1
2, 3, 6, 9, 10, 13, 16, 17, 20, 23, 24, 27, 30, 31, 34, 37, 38, 41, 44, 45, 48, 51, 52, 55, 58, 59, 62, 65, 66, 69, 72, 73, 76, 79, 80, 83, 86, 87, 90, 93, 94, 97, 100, 101, 104, 107, 108, 111, 114, 115, 118, 121, 122, 125, 128, 129, 132, 135, 136, 139, 142 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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+x+3*x^2+x^3) / ( (1+x+x^2)*(x-1)^2 ). - R. J. Mathar, Oct 25 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+4*sqrt(3)*sin(2*n*Pi/3))/9.

a(3k) = 7k-1, a(3k-1) = 7k-4, a(3k-2) = 7k-5. (End)

MAPLE

A047284:=n->(21*n-9+4*sqrt(3)*sin(2*n*Pi/3))/9: seq(A047284(n), n=1..100); # Wesley Ivan Hurt, Jun 07 2016

MATHEMATICA

Table[(21*n-9+4*Sqrt[3]*Sin[2*n*Pi/3])/9, {n, 80}] (* Wesley Ivan Hurt, Jun 07 2016 *)

PROG

(MAGMA) [n : n in [1..150] | n mod 7 in [2, 3, 6]]; // Wesley Ivan Hurt, Jun 07 2016

CROSSREFS

Sequence in context: A323393 A190674 A188399 * A268692 A089160 A214974

Adjacent sequences:  A047281 A047282 A047283 * A047285 A047286 A047287

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified October 20 18:19 EDT 2019. Contains 328269 sequences. (Running on oeis4.)