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 A257329 #13 Apr 30 2015 20:03:41 %S A257329 2,11,13,25,21,37,27,10,39,20,71,24,85,32,95,107,115,121,125,46,145, %T A257329 151,155,99,167,105,181,117,197,205,211,141,223,147,76,159,86,263,72, %U A257329 259,135,289,30,311,60,301,94,337,116,341,343,110,359,112,237,122,389 %N A257329 Construct spiral of numbers on square grid as in Comments; sequence gives terms along the "2" arm. %C A257329 Place numbers 2,3,5,7 clockwise around a grid point (see illustrations in links). Divide grid into four spiral arms. %C A257329 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 A257329 Rule for extending: next term in arm is smallest number such that each cell in the grid is relatively prime to its eight neighbors. Every term in the entire grid must be different. %C A257329 The four arms are A257329, A257330, A257331, A257332. %C A257329 Conjecture: every number > 1 appears in one of the four arms. %H A257329 Lars Blomberg, <a href="/A257329/b257329.txt">Table of n, a(n) for n = 1..10000</a> %H A257329 Popular Computing (Calabasas, CA), <a href="/A257321/a257321.png">Problem 146: Gcd</a>, Vol. 4 (No. 45, Dec 1976), page PC45-4. %H A257329 N. J. A. Sloane, <a href="/A257321/a257321_1.png">Spirals showing initial terms of A257321-A257332</a> %Y A257329 Cf. A064413, A257321-A257340, A257347 (the union list). %K A257329 nonn %O A257329 1,1 %A A257329 _N. J. A. Sloane_, Apr 21 2015 %E A257329 More terms from _Lars Blomberg_, Apr 27 2015