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Numbers that are congruent to {0, 2, 3, 4, 6} mod 8.
1

%I #25 Sep 08 2022 08:44:57

%S 0,2,3,4,6,8,10,11,12,14,16,18,19,20,22,24,26,27,28,30,32,34,35,36,38,

%T 40,42,43,44,46,48,50,51,52,54,56,58,59,60,62,64,66,67,68,70,72,74,75,

%U 76,78,80,82,83,84,86,88,90,91,92,94,96,98,99,100,102

%N Numbers that are congruent to {0, 2, 3, 4, 6} mod 8.

%H Vincenzo Librandi, <a href="/A047418/b047418.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,1,-1).

%F G.f.: x^2*(2 + x + x^2 + 2*x^3 + 2*x^4)/((x^4 + x^3 + x^2 + x + 1)*(x - 1)^2). - _R. J. Mathar_, Dec 05 2011

%F From _Wesley Ivan Hurt_, Aug 08 2016: (Start)

%F a(n) = a(n-1) + a(n-5) - a(n-6) for n > 6, a(n) = a(n-5) + 8 for n > 5.

%F a(n) = (40*n - 45 - 2*(n mod 5) + 3*((n + 1) mod 5) + 3*((n + 2) mod 5) - 2*((n + 3) mod 5) - 2*((n + 4) mod 5))/25.

%F a(5*k) = 8*k - 2, a(5*k-1) = 8*k - 4, a(5*k-2) = 8*k - 5, a(5*k-3) = 8*k - 6, a(5*k-4) = 8*k - 8. (End)

%F a(n) = (40*n - 45 + 2*cos(2*Pi*(n - 1)/5) - 2*cos(2*Pi*n/5) - 2*cos(4*Pi*n/5) - 6*cos(2*Pi*(n + 1)/5) - 6*cos(Pi*(2*n + 1)/5) + 6*cos(2*Pi*(2*n + 1)/5) - 2*cos(Pi*(4*n + 1)/5) + 6*sin(Pi*(8*n + 3)/10))/25. - _Wesley Ivan Hurt_, Oct 10 2018

%p A047418:=n->8*floor(n/5)+[(0, 2, 3, 4, 6)][(n mod 5)+1]: seq(A047418(n), n=0..100); # _Wesley Ivan Hurt_, Aug 08 2016

%t Select[Range[0,100], MemberQ[{0,2,3,4,6}, Mod[#,8]]&] (* or *) LinearRecurrence[{1,0,0,0,1,-1}, {0,2,3,4,6,8}, 70] (* _Harvey P. Dale_, Oct 01 2015 *)

%o (Magma) [n : n in [0..150] | n mod 8 in [0, 2, 3, 4, 6]]; // _Wesley Ivan Hurt_, Aug 08 2016

%o (GAP) Filtered([0..103],n->n mod 8 = 0 or n mod 8 = 2 or n mod 8 = 3 or n mod 8 = 4 or n mod 8 = 6); # _Muniru A Asiru_, Oct 23 2018

%Y Cf. A047412, A047434, A047486, A047489, A047501, A047511, A047584.

%K nonn,easy

%O 1,2

%A _N. J. A. Sloane_