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A047387 Numbers that are congruent to {1, 2, 5} mod 7. 1
1, 2, 5, 8, 9, 12, 15, 16, 19, 22, 23, 26, 29, 30, 33, 36, 37, 40, 43, 44, 47, 50, 51, 54, 57, 58, 61, 64, 65, 68, 71, 72, 75, 78, 79, 82, 85, 86, 89, 92, 93, 96, 99, 100, 103, 106, 107, 110, 113, 114, 117, 120, 121, 124, 127, 128, 131, 134, 135, 138, 141 (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*(1+x+3*x^2+2*x^3)/((1+x+x^2)*(x-1)^2). - R. J. Mathar, Dec 05 2011

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

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

a(n) = 7*n/3-2+4*sin(2*n*Pi/3)/(3*sqrt(3)).

a(3k) = 7k-2, a(3k-1) = 7k-5, a(3k-2) = 7k-6. (End)

MAPLE

A047387:=n->7*n/3-2+4*sin(2*n*Pi/3)/(3*sqrt(3)): seq(A047387(n), n=1..100); # Wesley Ivan Hurt, Jun 09 2016

MATHEMATICA

Select[Range[200], MemberQ[{1, 2, 5}, Mod[#, 7]]&] (* or *) LinearRecurrence[ {1, 0, 1, -1}, {1, 2, 5, 8}, 90] (* Harvey P. Dale, Jun 05 2014 *)

PROG

(MAGMA) [n : n in [0..150] | n mod 7 in [1, 2, 5]]; // Wesley Ivan Hurt, Jun 09 2016

CROSSREFS

Sequence in context: A183234 A108968 A289628 * A063282 A276882 A045928

Adjacent sequences:  A047384 A047385 A047386 * A047388 A047389 A047390

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified October 18 01:04 EDT 2019. Contains 328135 sequences. (Running on oeis4.)