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A048893
Threshold function for orthogonal arrays of strength 2.
1
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 6, 12, 13, 14, 15, 16, 15, 18, 11, 20, 21, 22
OFFSET
1,3
COMMENTS
a(n) = max b such that any parameter set satisfying the obvious necessary conditions and with <= b degrees of freedom exists, but some such parameter set with b+1 degrees of freedom does not exist.
LINKS
E. M. Rains, N. J. A. Sloane and J. Stufken, The Lattice of N-Run Orthogonal Arrays, J. Stat. Planning Inference, 102 (2002), 477-500 (Abstract, pdf, ps)
CROSSREFS
Sequence in context: A374485 A291751 A275987 * A330814 A305903 A305904
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, John Stufken (jstufken(AT)iastate.edu)
EXTENSIONS
18<=a(24)<=22 is the first open case. Sequence then continues 24,25,26,15,28,29,30,29.
STATUS
approved