A350795 - OEIS

%I #8 Jan 29 2022 22:31:11

%S 1,0,1,0,0,1,1,0,0,0,1,6,8,4,1,0,0,0,0,1,16,70,140,159,113,53,17,4,1,

%T 0,0,0,0,0,1,33,313,1439,3941,7297,9750,9840,7717,4788,2377,946,309,

%U 80,18,4,1,0,0,0,0,0,0,1,58,998,8447,43269,152135,396011

%N Triangle read by rows: T(n,k) is the number of digraphs on n unlabeled nodes with k arcs and a global source and sink, n >= 1, k = 0..max(1,n-1)*(n-2)+1.

%H Andrew Howroyd, <a href="/A350795/b350795.txt">Table of n, a(n) for n = 1..2319</a> (rows 1..20)

%e Triangle begins:

%e   [1] 1;

%e   [2] 0, 1;

%e   [3] 0, 0, 1, 1;

%e   [4] 0, 0, 0, 1, 6,  8,  4,   1;

%e   [5] 0, 0, 0, 0, 1, 16, 70, 140, 159, 113, 53, 17, 4, 1;

%e   ...

%o (PARI) \\ See PARI link in A350794 for program code.

%o { my(A=A350795triang(5)); for(n=1, #A, print(A[n])) }

%Y Row sums are A350794.

%Y Column sums are A350796.

%Y The labeled version is A350791.

%Y Cf. A057277, A057278, A350797.

%K nonn,tabf

%O 1,12

%A _Andrew Howroyd_, Jan 21 2022