A005048 Minimal span of set of n elements with no 4-term arithmetic progression.

4, 5, 7, 8, 9, 12, 14, 16, 18, 20, 22, 24, 26, 27, 29, 32, 33, 36, 39, 42, 44, 47, 49, 52, 53, 57, 59, 63, 65, 67, 69, 73, 76, 78, 81, 83, 86, 90, 92, 96, 98, 100, 103, 104, 106, 111, 113, 119, 121, 125, 128, 131, 133, 137, 140

Offset

4,1

Comments

If the first appearance of n in A003003 is A003003(k) = n, then a(n) = k-1. - Robert Israel, Mar 21 2016

Links

Table of n, a(n) for n=4..58.

B. E. Brown and D. M. Gordon, On sequences without geometric progressions, Math. Comp. 65 (1996), no. 216, 1749-1754.

Sean A. Irvine, Example sets for a(4)-a(27)

Example

Example for n=13: { 1, 2, 3, 5, 6, 8, 9, 10, 16, 17, 18, 20, 21 } with span 20.

Crossrefs

Cf. A005047, A005049, A005050.

Sequence in context: A189477 A047494 A080712 * A119642 A276705 A168044

Adjacent sequences: A005045 A005046 A005047 * A005049 A005050 A005051

Keyword

nonn,more

Author

N. J. A. Sloane

Extensions

Corrected and extended by David W. Wilson, May 15 1997

a(22)-a(26) from Sean A. Irvine, Mar 17 2016

a(24)-a(26) corrected by Robert Israel, Mar 20 2016

a(27) from Sean A. Irvine, Mar 20 2016

a(28)-a(34) from Robert Israel, Mar 21 2016

a(35)-a(58) from Fausto A. C. Cariboni, Jun 17 2018

Status

approved