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A350449 Triangle read by rows: T(n,k) is the number of weakly connected acyclic digraphs on n unlabeled nodes with k arcs, n >= 1, k = 0..(n-1)*n/2.

%I A350449 #11 Jan 09 2022 13:02:59
%S A350449 1,0,1,0,0,3,1,0,0,0,8,9,6,1,0,0,0,0,27,54,79,63,33,10,1,0,0,0,0,0,91,
%T A350449 320,732,1136,1281,1056,649,281,85,15,1,0,0,0,0,0,0,350,1788,6012,
%U A350449 14378,26529,38407,44621,41638,31321,18843,8983,3325,920,180,21,1
%N A350449 Triangle read by rows: T(n,k) is the number of weakly connected acyclic digraphs on n unlabeled nodes with k arcs, n >= 1, k = 0..(n-1)*n/2.
%H A350449 Andrew Howroyd, <a href="/A350449/b350449.txt">Table of n, a(n) for n = 1..1350</a> (rows 1..20)
%e A350449 Triangle begins:
%e A350449   [1] 1;
%e A350449   [2] 0, 1;
%e A350449   [3] 0, 0, 3, 1;
%e A350449   [4] 0, 0, 0, 8,  9,  6,  1;
%e A350449   [5] 0, 0, 0, 0, 27, 54, 79, 63, 33, 10, 1;
%e A350449   ...
%o A350449 (PARI) \\ See PARI link in A122078 for program code.
%o A350449 { my(T=WeakAcyclicDigraphsByArcs(6)); for(n=1, #T, print(T[n])) }
%Y A350449 Row sums are A101228.
%Y A350449 Columns sums are A350451.
%Y A350449 Leading diagonal is A000238.
%Y A350449 Cf. A350447 (not necessarily connected), A350450 (transpose).
%K A350449 nonn,tabf
%O A350449 1,6
%A A350449 _Andrew Howroyd_, Dec 31 2021