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 A257323 #12 Apr 28 2015 11:01:53 %S A257323 5,2,11,2,5,7,2,5,7,3,5,3,5,3,7,3,2,11,3,5,7,2,7,2,7,2,5,2,3,2,5,2,5, %T A257323 7,3,7,3,5,3,5,7,2,5,7,3,7,3,7,3,2,11,3,5,3,5,3,5,3,7,3,2,5,2,5,2,7,2, %U A257323 7,2,3,5,7,2,7,2,7,2,7,2,5,7,3,5,11,2,5 %N A257323 Construct spiral of numbers on square grid as in Comments; sequence gives terms along the "5" arm. %C A257323 Place numbers 2,3,5,7 clockwise around a grid point (see illustrations in links). Divide grid into four spiral arms. %C A257323 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 A257323 Rule for extending: next term in arm is smallest number such that each cell in the grid is relatively prime to its eight neighbors. %C A257323 Repetitions in arms are permitted. %C A257323 The four arms are A257321, A257322, A257323, A257324. %H A257323 Lars Blomberg, <a href="/A257323/b257323.txt">Table of n, a(n) for n = 1..10000</a> %H A257323 Popular Computing (Calabasas, CA), <a href="/A257321/a257321.png">Problem 146: Gcd</a>, Vol. 4 (No. 45, Dec 1976), page PC45-4. %H A257323 N. J. A. Sloane, <a href="/A257321/a257321_1.png">Spirals showing initial terms of A257321-A257332</a> %Y A257323 Cf. A064413, A257321-A257340. %K A257323 nonn %O A257323 1,1 %A A257323 _N. J. A. Sloane_, Apr 21 2015 %E A257323 More terms from _Lars Blomberg_, Apr 27 2015