This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A139438 #8 Jun 05 2016 23:53:18 %S A139438 1,1,2,3,1,1,3,5,2,1,1,2,1,1,1,1,1,2,3,1,1,3,5,2,1,1,2,1,1,1,1,1,2,3, %T A139438 1,1,3,5,2,1,1,2,1,1,1,1,1,2,3,1,1,3,5,2,1,1,2,1,1,1,1,1,2,3,1,1,3,5, %U A139438 2,1,1,2,1,1,1,1,1,2,3,1,1,3,5,2,1,1,2,1,1,1,1,1,2,3,1,1,3,5,2 %N A139438 Frieze pattern with 5 rows, read by diagonals. %C A139438 Period 15: repeat [1, 1, 2, 3, 1, 1, 3, 5, 2, 1, 1, 2, 1, 1, 1]. - _Wesley Ivan Hurt_, Jun 05 2016 %H A139438 James Propp, <a href="http://arxiv.org/abs/math/0511633">The combinatorics of frieze patterns and Markoff numbers</a>, arXiv:math/0511633v4. %F A139438 Four adjacent entries %F A139438 ...A... %F A139438 .B...C. %F A139438 ...D... %F A139438 satisfy D = (BC-1)/A. %e A139438 The frieze pattern is %e A139438 ... 1 1 1 1 1 1 1 ... %e A139438 .....1 3 2 1 3 2 ... %e A139438 ....1 2 5 1 2 5 1 ... %e A139438 .....1 3 2 1 3 2 ... %e A139438 ... 1 1 1 1 1 1 1 ... %Y A139438 Cf. A139434, A139458. %K A139438 nonn,tabf %O A139438 0,3 %A A139438 _N. J. A. Sloane_, Jun 09 2008