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A350447 Triangle read by rows: T(n,k) is the number of acyclic digraphs on n unlabeled nodes with k arcs, n >=0, k = 0..(n-1)*n/2.

%I A350447 #12 Jan 09 2022 12:43:47
%S A350447 1,1,1,1,1,1,3,1,1,1,4,9,9,6,1,1,1,4,12,37,60,80,63,33,10,1,1,1,4,13,
%T A350447 51,163,407,796,1169,1291,1057,649,281,85,15,1,1,1,4,13,54,215,846,
%U A350447 2690,7253,15703,27596,39057,44902,41723,31336,18844,8983,3325,920,180,21,1
%N A350447 Triangle read by rows: T(n,k) is the number of acyclic digraphs on n unlabeled nodes with k arcs, n >=0, k = 0..(n-1)*n/2.
%H A350447 Andrew Howroyd, <a href="/A350447/b350447.txt">Table of n, a(n) for n = 0..1350</a> (rows 0..20)
%e A350447 Triangle begins:
%e A350447   [0] 1;
%e A350447   [1] 1;
%e A350447   [2] 1, 1;
%e A350447   [3] 1, 1, 3,  1;
%e A350447   [4] 1, 1, 4,  9,  9,  6,  1;
%e A350447   [5] 1, 1, 4, 12, 37, 60, 80, 63, 33, 10, 1;
%e A350447   ...
%o A350447 (PARI) \\ See PARI link in A122078 for program code.
%o A350447 { my(T=AcyclicDigraphsByArcs(6)); for(n=1, #T, print(T[n])) }
%Y A350447 The labeled version is A081064.
%Y A350447 Row sums are A003087.
%Y A350447 Cf. A122078, A350449.
%K A350447 nonn,tabf
%O A350447 0,7
%A A350447 _Andrew Howroyd_, Dec 31 2021