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Period 9: repeat [1, 2, 3, 4, 5, 4, 3, 2, 1].
1

%I #22 Dec 12 2023 08:47:25

%S 1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,

%T 2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,

%U 4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5

%N Period 9: repeat [1, 2, 3, 4, 5, 4, 3, 2, 1].

%H Vincenzo Librandi, <a href="/A134011/b134011.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,1).

%F a(n) = a(n-9) for n > 8. G.f.: (1 + x + x^2 + x^3 + x^4)^2/(1 - x^9). - _Chai Wah Wu_, Jun 04 2016

%p A134011:=n->[1, 2, 3, 4, 5, 4, 3, 2, 1][(n mod 9)+1]: seq(A134011(n), n=0..100); # _Wesley Ivan Hurt_, Jun 11 2016

%t PadRight[{}, 81, {1,2,3,4,5,4,3,2,1}] (* _Harvey P. Dale_, Oct 31 2011 *)

%o (Magma) &cat [[1, 2, 3, 4, 5, 4, 3, 2, 1]: n in [0..8]]; // _Wesley Ivan Hurt_, Jun 11 2016

%Y Cf. A131974.

%K nonn,easy

%O 0,2

%A _Paul Curtz_, Jan 10 2008