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 A257339 #41 Apr 29 2015 16:06:55 %S A257339 1,2,3,5,4,7,6,11,9,13,17,19,8,23,29,21,25,31,37,41,35,43,47,10,49,12, %T A257339 53,14,15,59,27,55,39,16,61,22,51,67,18,65,24,71,26,33,32,57,73,79,83, %U A257339 77,85,89,97,101,28,95,34,91,38,103,107,45,109,113,20,121 %N A257339 Arrange numbers in a single clockwise spiral so that each number is relatively prime to its eight neighbors. %C A257339 Start with 1; always choose smallest number which has not yet appeared. %C A257339 It is conjectured that every number appears. %H A257339 Jon E. Schoenfield and Reinhard Zumkeller, <a href="/A257339/b257339.txt">Table of n, a(n) for n = 1..100000</a> (First 10000 terms from Jon E. Schoenfield) %H A257339 Jon E. Schoenfield, <a href="/A257339/a257339_1.png">Illustration of initial terms</a> %H A257339 Jon E. Schoenfield, <a href="/A257339/a257339_2.png">Graph of first 18000 terms</a> %Y A257339 Cf. A064413, A257321-A257340. %Y A257339 Cf. A257111 (first differences), A257455 (putative inverse). %Y A257339 Indices of primes and prime powers: A257457 and A257458. %K A257339 nonn %O A257339 1,2 %A A257339 _N. J. A. Sloane_, Apr 21 2015 %E A257339 Corrected and extended by _Jon E. Schoenfield_, Apr 23 2015