This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A048893 #5 Oct 04 2012 10:28:38 %S A048893 0,1,2,3,4,5,6,7,8,9,10,6,12,13,14,15,16,15,18,11,20,21,22 %N A048893 Threshold function for orthogonal arrays of strength 2. %C A048893 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. %H A048893 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 (<a href="http://neilsloane.com/doc/rao.txt">Abstract</a>, <a href="http://neilsloane.com/doc/rao.pdf">pdf</a>, <a href="http://neilsloane.com/doc/rao.ps">ps</a>) %Y A048893 Cf. A048894, A048885. %K A048893 nonn %O A048893 1,3 %A A048893 _N. J. A. Sloane_, John Stufken (jstufken(AT)iastate.edu) %E A048893 18<=a(24)<=22 is the first open case. Sequence then continues 24,25,26,15,28,29,30,29.