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%I #17 Aug 15 2017 13:52:51
%S 1,1,1,2,4,9,22,60,176,565,1980,7528,30843,135248,630004,3097780,
%T 15991395,86267557,484446620,2822677523,17017165987
%N Number of graded lattices on n nodes.
%C A finite lattice is graded if, for any element, all paths from the bottom to that element have the same length.
%H J. Heitzig and J. Reinhold, <a href="http://dx.doi.org/10.1007/PL00013837">Counting finite lattices</a>, Algebra Universalis, 48 (2002), 43-53.
%H J. Kohonen, <a href="http://arxiv.org/abs/1708.03750">Generating modular lattices up to 30 elements</a>, arXiv:1708.03750 [math.CO] preprint (2017).
%H M. Malandro, <a href="http://www.shsu.edu/mem037/Lattices.html">The unlabeled lattices on <=15 nodes</a>, (listing of lattices; graded lattices are a subset of these).
%Y Cf. A006966 (lattices), A229202 (semimodular lattices).
%K nonn,more
%O 1,4
%A _Jukka Kohonen_, Nov 26 2016
%E a(16)-a(21) from Kohonen (2017), by _Jukka Kohonen_, Aug 15 2017
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