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 A257326 #9 Apr 27 2015 10:44:58 %S A257326 3,2,7,9,5,13,15,17,11,4,19,23,21,25,8,29,10,31,14,37,16,41,22,43,47, %T A257326 27,53,55,26,35,33,49,59,61,67,71,65,73,77,79,83,39,89,97,101,32,103, %U A257326 20,91,34,107,40,109,38,51,113,57,28,85,44,119,46,81,121,45 %N A257326 Construct spiral of numbers on square grid as in Comments; sequence gives terms along the "3" arm. %C A257326 Place numbers 2,3,5,7 clockwise around a grid point (see illustrations in links). Divide grid into four spiral arms. %C A257326 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 A257326 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 A257326 Repetitions between arms are permitted. %C A257326 The four arms are A257325, A257326, A257327, A257328. %H A257326 Lars Blomberg, <a href="/A257326/b257326.txt">Table of n, a(n) for n = 1..10000</a> %H A257326 Popular Computing (Calabasas, CA), <a href="/A257321/a257321.png">Problem 146: Gcd</a>, Vol. 4 (No. 45, Dec 1976), page PC45-4. %H A257326 N. J. A. Sloane, <a href="/A257321/a257321_1.png">Spirals showing initial terms of A257321-A257332</a> %Y A257326 Cf. A064413, A257321-A257340. %K A257326 nonn %O A257326 1,1 %A A257326 _N. J. A. Sloane_, Apr 21 2015 %E A257326 More terms from _Lars Blomberg_, Apr 27 2015