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 A225859 #21 May 25 2018 13:36:13
%S A225859 1,2,3,4,6,7,8,9,11,12,13,14,16,17,18,19,24,25,27,28,29,31,33,34,36,
%T A225859 37,38,39,41,42,43,44,49,51,52,54,56,57,58,59,61,62,63,64,66,67,68,69,
%U A225859 76
%N A225859 Smallest k such that n numbers can be picked in {1,...,k} with no five terms in arithmetic progression.
%D A225859 Knuth, Donald E., Satisfiability, Fascicle 6, volume 4 of The Art of Computer Programming. Addison-Wesley, 2015, pages 135 and 190, Problem 31.
%H A225859 Samuel S. Wagstaff, Jr., <a href="http://dx.doi.org/10.1090/S0025-5718-1972-0325500-5">On k-free sequences of integers</a>, Math. Comp., 26 (1972), 767-771.
%Y A225859 This sequence is to A003004 as A065825 is to A003002.
%Y A225859 Cf. A226066.
%K A225859 nonn,more
%O A225859 1,2
%A A225859 _Don Knuth_, Aug 05 2013