%I A056941
%S A056941 1,1,1,1,6,1,1,21,21,1,1,56,196,56,1,1,126,1176,1176,126,1,1,252,5292,
%T A056941 14112,5292,252,1,1,462,19404,116424,116424,19404,462,1,1,792,60984,
%U A056941 731808,1646568,731808,60984,792,1,1,1287,169884,3737448,16818516
%N A056941 Antichains (or order ideals) in the poset 5*m*n or plane partitions with 
               rows <= m, columns <= n and entries <= 5
%D A056941 Berman and Koehler, Cardinalities of finite distributive lattices, Mitteilungen 
               aus dem Mathematischen Seminar Giessen, 121 (1976), p. 103-124
%D A056941 P. A. MacMahon, Combinatory Analysis, Section 495, 1916.
%D A056941 R. P. Stanley, Theory and application of plane partitions. II. Studies 
               in Appl. Math. 50 (1971), p. 259-279. Thm. 18.1
%H A056941 P. A. MacMahon, <a href="http://www.hti.umich.edu/cgi/t/text/text-idx?c=umhistmath;
               idno=ABU9009">Combinatory analysis</a>.
%H A056941 <a href="Sindx_Pos.html#posets">Index entries for sequences related to 
               posets</a>
%F A056941 Product[ C(n+m+k, m+k)/C(n+k, k), {k, 0, 4} ]
%Y A056941 Cf. A000372, A056932, A001263, A056939, A056940.
%Y A056941 Antidiagonals sum to A005363 (Hoggatt sequence)
%Y A056941 Sequence in context: A146988 A060972 A144066 this_sequence A157638 A142596 
               A155467
%Y A056941 Adjacent sequences: A056938 A056939 A056940 this_sequence A056942 A056943 
               A056944
%K A056941 nonn,easy,tabl
%O A056941 0,5
%A A056941 Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu)