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Smallest k such that n numbers can be picked in {1,...,k} with no six terms in arithmetic progression.
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%I #18 May 25 2018 13:38:24

%S 1,2,3,4,5,7,8,9,10,12,13,14,15,17,18,19,20,22,23,24,25,26,29,32,33,

%T 35,36,37,39,40,41,44,45,46,48,49,50,51,54,56,58,59,61,62

%N Smallest k such that n numbers can be picked in {1,...,k} with no six terms in arithmetic progression.

%D Knuth, Donald E., Satisfiability, Fascicle 6, volume 4 of The Art of Computer Programming. Addison-Wesley, 2015, pages 135 and 190, Problem 31.

%H 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 This sequence is to A003005 as A065825 is to A003002.

%Y Cf. A225745, A225859.

%K nonn,more

%O 1,2

%A _Don Knuth_, Aug 05 2013