A047311 - OEIS

A047311

Numbers that are congruent to {4, 5, 6} mod 7.

4, 5, 6, 11, 12, 13, 18, 19, 20, 25, 26, 27, 32, 33, 34, 39, 40, 41, 46, 47, 48, 53, 54, 55, 60, 61, 62, 67, 68, 69, 74, 75, 76, 81, 82, 83, 88, 89, 90, 95, 96, 97, 102, 103, 104, 109, 110, 111, 116, 117, 118, 123, 124, 125, 130, 131, 132, 137, 138, 139, 144

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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*(4+x+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+3-12*cos(2*n*Pi/3)+4*sqrt(3)*sin(2*n*Pi/3))/9.

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