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

%I #31 Jan 26 2024 15:14:51

%S 1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,

%T 3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,

%U 1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3,1,2,2,1,3

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

%C This sequence (if extended to be bi-infinite) is the quiddity sequence of the unique width-5 Coxeter frieze pattern A139434; equivalently, if one goes around the (uniquely) triangulated regular pentagon and sequentially looks at its vertices, counting the number of triangles incident with each vertex, then this sequence will be obtained. - _Andrey Zabolotskiy_, May 04 2023

%H G. C. Greubel, <a href="/A135352/b135352.txt">Table of n, a(n) for n = 1..1000</a>

%H Karin Baur, <a href="https://doi.org/10.1007/s00283-021-10065-x">Frieze Patterns of Integers</a>, Math. Intelligencer 43, 47-54 (2021). See Example 2 and Figure 4.

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,1).

%Y Cf. A076839, A139434.

%K nonn,easy

%O 1,2

%A _Roger L. Bagula_, Feb 16 2008

%E Edited by _Joerg Arndt_, Oct 11 2016

%E Initial term 1 removed by _Joerg Arndt_, May 04 2023