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 A257330 #11 Apr 30 2015 20:04:04 %S A257330 3,4,17,29,31,41,49,33,61,18,73,51,77,57,28,109,34,127,38,87,62,157, %T A257330 40,163,169,175,187,193,64,209,203,221,227,239,153,245,171,269,177, %U A257330 281,293,299,189,313,201,106,207,70,219,100,347,84,361,96,379,243,391 %N A257330 Construct spiral of numbers on square grid as in Comments; sequence gives terms along the "3" arm. %C A257330 Place numbers 2,3,5,7 clockwise around a grid point (see illustrations in links). Divide grid into four spiral arms. %C A257330 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 A257330 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 A257330 The four arms are A257329, A257330, A257331, A257332. %C A257330 Conjecture: every number > 1 appears in one of the four arms. %H A257330 Lars Blomberg, <a href="/A257330/b257330.txt">Table of n, a(n) for n = 1..10000</a> %H A257330 Popular Computing (Calabasas, CA), <a href="/A257321/a257321.png">Problem 146: Gcd</a>, Vol. 4 (No. 45, Dec 1976), page PC45-4. %H A257330 N. J. A. Sloane, <a href="/A257321/a257321_1.png">Spirals showing initial terms of A257321-A257332</a> %Y A257330 Cf. A064413, A257321-A257340, A257347 (the union list). %K A257330 nonn %O A257330 1,1 %A A257330 _N. J. A. Sloane_, Apr 21 2015 %E A257330 More terms from _Lars Blomberg_, Apr 27 2015