%I #20 Oct 09 2019 20:57:10
%S 0,1,1,3,3,4,4,4,4,6,6,6,7,7,7,9,9,9,10,10,10,12,12,12,13,13,13
%N Column 3 of array in A318240.
%C The next value a(28) is either 15 or 16.
%C a(6k+1) = a(6k+2) = a(6k+3) = 3k+1 for k >= 1. This follows from the solution to Kirkman's schoolgirl problem with n schoolgirls.
%C The values of a(6k), a(6k-1) and a(6k-2) are either 3k or 3k+1.
%H D. K. Ray-Chaudhuri and Richard M. Wilson, <a href="https://doi.org/10.1090/pspum/019">Solution of Kirkman's schoolgirl problem</a>, in Proceedings of Symposia in Pure Mathematics, Volume 19, 1971.
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Kirkman%27s_schoolgirl_problem">Kirkman's schoolgirl problem</a>
%Y Cf. A318240.
%K nonn,more
%O 1,4
%A _Floris P. van Doorn_, Aug 25 2018
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