|
%I #12 Jan 22 2022 23:42:30
%S 1,0,1,1,0,0,1,4,4,1,1,0,0,0,1,11,31,45,38,27,13,5,1,1,0,0,0,0,1,23,
%T 152,486,992,1419,1641,1485,1152,707,379,154,61,16,5,1,1,0,0,0,0,0,1,
%U 42,517,3194,12174,32860,68423,116168,166164,204867,219906,206993,170922,124088,78809,43860,21209,8951,3242,1043,288,76,17,5,1,1
%N Triangle T(n,k) of number of digraphs with a source and a sink on n unlabeled nodes and k arcs, k=0..n*(n-1).
%D V. Jovovic, G. Kilibarda, Enumeration of labeled initially-finally connected digraphs, Scientific review, Serbian Scientific Society, 19-20 (1996), p. 246.
%H Andrew Howroyd, <a href="/A057278/b057278.txt">Table of n, a(n) for n = 1..2680</a> (rows 1..20)
%e Triangle begins:
%e [1],
%e [0,1,1],
%e [0,0,1,4,4,1,1],
%e [0,0,0,1,11,31,45,38,27,13,5,1,1],
%e ...
%e The number of digraphs with a source and a sink on 3 unlabeled nodes is 11 = 1+4+4+1+1.
%o (PARI) \\ See PARI link in A350794 for program code.
%o { my(A=A057278triang(5)); for(n=1, #A, print(A[n])) } \\ _Andrew Howroyd_, Jan 21 2022
%Y Row sums give A049531.
%Y Column sums give A350906.
%Y The labeled version is A057271.
%Y Cf. A057270, A057276, A057277, A057279, A350794, A350795.
%K nonn,tabf
%O 1,8
%A _Vladeta Jovovic_, Goran Kilibarda, Sep 14 2000
%E Terms a(46) and beyond from _Andrew Howroyd_, Jan 21 2022
|
