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 A257327 #9 Apr 27 2015 10:42:17 %S A257327 5,2,11,4,7,13,8,17,19,3,23,9,29,21,31,15,14,37,27,41,43,16,33,26,25, %T A257327 6,47,12,53,22,49,10,39,35,51,59,57,61,63,65,67,20,71,73,69,79,45,83, %U A257327 85,28,89,97,77,75,91,55,81,101,87,95,32,103,38,107,18,109 %N A257327 Construct spiral of numbers on square grid as in Comments; sequence gives terms along the "5" arm. %C A257327 Place numbers 2,3,5,7 clockwise around a grid point (see illustrations in links). Divide grid into four spiral arms. %C A257327 Extend each arm one step at a time, in rotation: first the 2 arm, then the 3 arm, then the 5 arm, then the 7 arm, then the 2 arm, etc. %C A257327 Rule for extending: next term in arm is smallest number such that each cell in the grid is relatively prime to its eight neighbors. Inside an arm, the terms must be distinct. %C A257327 Repetitions between arms are permitted. %C A257327 The four arms are A257325, A257326, A257327, A257328. %H A257327 Lars Blomberg, <a href="/A257327/b257327.txt">Table of n, a(n) for n = 1..10000</a> %H A257327 Popular Computing (Calabasas, CA), <a href="/A257321/a257321.png">Problem 146: Gcd</a>, Vol. 4 (No. 45, Dec 1976), page PC45-4. %H A257327 N. J. A. Sloane, <a href="/A257321/a257321_1.png">Spirals showing initial terms of A257321-A257332</a> %Y A257327 Cf. A064413, A257321-A257340. %K A257327 nonn %O A257327 1,1 %A A257327 _N. J. A. Sloane_, Apr 21 2015 %E A257327 More terms from _Lars Blomberg_, Apr 27 2015