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A005048 Minimal span of set of n elements with no 4-term arithmetic progression. 3
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified March 26 00:37 EDT 2019. Contains 321479 sequences. (Running on oeis4.)