A048893 Threshold function for orthogonal arrays of strength 2.

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

Author

N. J. A. Sloane, John Stufken (jstufken(AT)iastate.edu)

Keywords

• nonn

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

Cf. A048894, A048885.

Extensions

18<=a(24)<=22 is the first open case. Sequence then continues 24,25,26,15,28,29,30,29.