

A225745


Smallest k such that n numbers can be picked in {1,...,k} with no four in arithmetic progression.


2



1, 2, 3, 5, 6, 8, 9, 10, 13, 15, 17, 19, 21, 23, 25, 27, 28, 30, 33, 34, 37, 40, 43, 45, 48, 50, 53, 54, 58, 60, 64, 66, 68, 70, 74, 77
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OFFSET

1,2


REFERENCES

Knuth, Donald E., Satisfiability, Fascicle 6, volume 4 of The Art of Computer Programming. AddisonWesley, 2015, pages 135 and 190, Problem 31.


LINKS

Table of n, a(n) for n=1..36.
Samuel S. Wagstaff, Jr., On kfree sequences of integers, Math. Comp., 26 (1972), 767771.


EXAMPLE

a(8)=10 because of the unique solution 1 2 3 5 6 8 9 10.


CROSSREFS

This sequence is to A003003 as A065825 is to A003002.
Sequence in context: A288373 A087067 A166018 * A238896 A190842 A273106
Adjacent sequences: A225742 A225743 A225744 * A225746 A225747 A225748


KEYWORD

nonn,more


AUTHOR

Don Knuth, Aug 05 2013


STATUS

approved



