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 A257336 #9 Apr 28 2015 11:00:21 %S A257336 3,8,11,14,25,22,21,26,33,34,45,44,59,48,67,58,69,68,79,66,89,84,97, %T A257336 90,103,98,113,106,115,108,127,128,133,132,145,138,151,144,161,150, %U A257336 169,162,175,176,183,178,189,188,195,194,209,202,219,208,227,216,235 %N A257336 Construct spiral of numbers on square grid as in Comments; sequence gives terms along the "3" arm. %C A257336 Place numbers 2,3,4,5 clockwise around a grid point (see illustration in "Spiral" link). Divide grid into four spiral arms. %C A257336 Extend each arm one step at a time, in rotation: first the 2 arm, then the 3 arm, then the 4 arm, then the 5 arm, then the 2 arm, etc. %C A257336 Rule for extending: next term in arm is smallest number such that each cell in the grid is relatively prime to its four (N,S,E,W) neighbors. Every term in the entire grid must be different. %C A257336 The four arms are A257335, A257336, A257337, A257338. %C A257336 Conjecture: every number > 1 appears in one of the four arms. %H A257336 Lars Blomberg, <a href="/A257336/b257336.txt">Table of n, a(n) for n = 1..10000</a> %H A257336 Popular Computing (Calabasas, CA), <a href="/A257321/a257321.png">Problem 146: Gcd</a>, Vol. 4 (No. 45, Dec 1976), page PC45-4. %H A257336 N. J. A. Sloane, <a href="/A257335/a257335.png">Spiral showing initial terms of A257335-A257338</a> %Y A257336 Cf. A064413, A257321-A257340. %K A257336 nonn %O A257336 1,1 %A A257336 _N. J. A. Sloane_, Apr 21 2015 %E A257336 Corrected a(5)-a(9) and more terms from _Lars Blomberg_, Apr 28 2015