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%I #25 Feb 27 2024 03:02:42
%S 7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,
%T 2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,
%U 7,5,2,4,7,5,2,4,7,5,2,4,7,5,2,4,7,5
%N Period 4: repeat [7, 5, 2, 4].
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,-1,1).
%F a(n) = A135536(n) mod 9.
%F O.g.f.: ((x+5)/(x^2+1)+9*(1-x))/2. a(n) = ((-1)^floor(n/2) * A010686(n+1) + 9)/2. - _R. J. Mathar_, Feb 23 2008
%F From _Wesley Ivan Hurt_, Jul 08 2016: (Start)
%F a(n) = a(n-1) - a(n-2) + a(n-3) for n>2, a(n) = a(n-4) for n>3.
%F a(n) = A021408(n) for n>1. (End)
%p seq(op([7, 5, 2, 4]), n=0..50); # _Wesley Ivan Hurt_, Jul 08 2016
%t Flatten[Table[{7,5,2,4},{20}]] (* _Harvey P. Dale_, Jun 22 2011 *)
%o (Magma) &cat [[7, 5, 2, 4]^^30]; // _Wesley Ivan Hurt_, Jul 08 2016
%Y Cf. A010686, A010693, A021408, A135536.
%K nonn,easy
%O 0,1
%A _Paul Curtz_, Feb 22 2008
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