A047378 - OEIS

A047378

Numbers that are congruent to {2, 4, 5} mod 7.

2, 4, 5, 9, 11, 12, 16, 18, 19, 23, 25, 26, 30, 32, 33, 37, 39, 40, 44, 46, 47, 51, 53, 54, 58, 60, 61, 65, 67, 68, 72, 74, 75, 79, 81, 82, 86, 88, 89, 93, 95, 96, 100, 102, 103, 107, 109, 110, 114, 116, 117, 121, 123, 124, 128, 130, 131, 135, 137, 138, 142

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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*(2+2*x+x^2+2*x^3)/((1+x+x^2)*(x-1)^2). - R. J. Mathar, Dec 04 2011

From Wesley Ivan Hurt, Jun 09 2016: (Start)

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

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

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