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%I #10 Mar 17 2015 15:52:29
%S 1,1,1,1,1,2,4,2,1,1,3,10,12,10,3,1,1,4,21,49,78,49,21,4,1,1,5,39,172,
%T 584,778,584,172,39,5,1,1,6,68,573,5236,18033,46661,18033,5236,573,68,
%U 6,1,1,7,112,1890,72205,971573,149636721,19498369,149636721,971573,72205,1890,112,7,1
%N Triangular array of numbers of 2-polymatroids of rank k on n unlabeled points, for n>=0, 0<=k<=2n.
%C The rows are symmetric: a(n,k) = a(n,2n-k).
%C Starting with n=7, the rows are not unimodal.
%H Thomas J. Savitsky, <a href="http://epubs.siam.org/doi/abs/10.1137/140955094">Enumeration of 2-polymatroids on up to seven elements</a>. SIAM J. Discrete Math., 28(4):1641-1650, 2014. <a href="http://arxiv.org/abs/1401.8006">arXiv:1401.8006</a>
%e Triangle starts with:
%e n=0: 1
%e n=1: 1 1 1
%e n=2: 1 2 4 2 1
%e n=3: 1 3 10 12 10 3 1
%e n=4: 1 4 21 49 78 49 21 4 1
%e n=5: 1 5 39 172 584 778 584 172 39 5 1
%e n=6: 1 6 68 573 5236 18033 46661 18033 5236 573 68 6 1
%e n=7: 1 7 112 1890 72205 971573 149636721 19498369 149636721 971573 72205 1890 112 7 1
%Y Cf. A256157, A256158, A256159, A053534
%K nonn,tabf
%O 0,6
%A _Max Alekseyev_, Mar 16 2015
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