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 A287655 #10 May 30 2017 00:21:58
%S A287655 0,1,2,3,4,5,6,7,6,5,4,3,2,1,2,3,4,5,6,7,8,7,6,5,4,3,2,3,4,5,6,7,8,9,
%T A287655 8,7,6,5,4,3,4,5,6,7,8,9,10,9,8,7,6,5,4,5,6,7,8,9,10,11,10,9,8,7,6,5,
%U A287655 6,7,8,9,10,11,12,11,10,9,8,7,6,7,8,9,10
%N A287655 Seven steps forward, six steps back.
%H A287655 <a href="/index/Rec#order_14">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,0,0,0,0,0,0,0,1,-1).
%F A287655 a(n) = a(n-1) + a(n-13) - a(n-14) for n > 13.
%F A287655 a(n) = Sum_{i=1..n} (-1)^floor((2*i-2)/13).
%p A287655 A287655:=n->add((-1)^floor((2*i-2)/13), i=1..n): seq(A287655(n), n=0..200);
%t A287655 Table[Sum[(-1)^Floor[(2 i - 2)/13], {i, n}], {n, 0, 100}]
%Y A287655 Cf. A008611 (one step back, two steps forward).
%Y A287655 Cf. A058207 (three steps forward, two steps back).
%Y A287655 Cf. A260644 (four steps forward, three steps back).
%Y A287655 Cf. A271800 (five steps forward, four steps back).
%Y A287655 Cf. A271859 (six steps forward, five steps back).
%K A287655 nonn,easy
%O A287655 0,3
%A A287655 _Wesley Ivan Hurt_, May 29 2017