A225745 Smallest k such that n numbers can be picked in {1,...,k} with no four in arithmetic progression.

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, 79, 82, 84, 87, 91

Offset

1,2

References

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

Links

Table of n, a(n) for n=1..41.

Samuel S. Wagstaff, Jr., On k-free sequences of integers, Math. Comp., 26 (1972), 767-771.

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

Extensions

a(37)-a(41) from Bert Dobbelaere, Sep 16 2020

Status

approved