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 A079421 #8 Aug 13 2025 22:25:17 %S A079421 0,1,1,1,1,1,1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,0,1,0,1,1,0,0,0,0,1,1, %T A079421 0,0,0,0,1,1,0,0,0,0,1,1,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1, %U A079421 0,0,0,0,0,0,0,1,0,1 %N A079421 Spiro-Fibonacci differences, a(n) = difference of two previous terms that are nearest when terms arranged in a spiral. %H A079421 Sean A. Irvine, <a href="/A079421/b079421.txt">Table of n, a(n) for n = 0..10000</a> %H A079421 N. Fernandez, <a href="http://www.borve.org/primeness/spirofib.html">Graphical representations of some Spiro-Fibonacci sequences</a> %e A079421 Terms are written in square boxes radiating spirally (cf. Ulam prime spiral). a(0)=0 and a(1)=1, so write 0 and then 1 to its right. a(2) goes in the box below a(1). The nearest two filled boxes contain a(0) and a(1), so a(2)=abs(a(0)-a(1))=abs(0-1)=1. a(3) goes in the box to the left of a(2). The nearest two filled boxes contain a(0) and a(2), so a(3)=abs(a(0)-a(2))=abs(0-1)=1. %Y A079421 Cf. A063826, A078510. %K A079421 nonn %O A079421 0,1 %A A079421 _Neil Fernandez_, Jan 07 2003