cp's OEIS Frontend

A057277 Triangle T(n,k) of number of digraphs with a source on n unlabeled nodes with k arcs, k=0..n*(n-1).

%I A057277 #11 Jan 22 2022 23:42:24
%S A057277 1,0,1,1,0,0,2,4,4,1,1,0,0,0,4,16,34,46,38,27,13,5,1,1,0,0,0,0,9,56,
%T A057277 229,573,1058,1448,1653,1487,1153,707,379,154,61,16,5,1,1,0,0,0,0,0,
%U A057277 20,198,1218,5089,15596,37302,72776,119531,168233,205923,220337,207147,170965,124099,78811,43861,21209,8951,3242,1043,288,76,17,5,1,1
%N A057277 Triangle T(n,k) of number of digraphs with a source on n unlabeled nodes with k arcs, k=0..n*(n-1).
%H A057277 Andrew Howroyd, <a href="/A057277/b057277.txt">Table of n, a(n) for n = 1..2680</a> (rows 1..20)
%e A057277 Triangle begins:
%e A057277   [1],
%e A057277   [0, 1, 1],
%e A057277   [0, 0, 2, 4, 4, 1, 1],
%e A057277   [0, 0, 0, 4, 16, 34, 46, 38, 27, 13, 5, 1, 1],
%e A057277   ....
%e A057277 The number of digraphs with a source on 3 unlabeled nodes is 12 = 2+4+4+1+1.
%o A057277 (PARI) \\ See PARI link in A350794 for program code.
%o A057277 { my(A=A057277triang(5)); for(n=1, #A, print(A[n])) } \\ _Andrew Howroyd_, Jan 21 2022
%Y A057277 Row sums give A051421.
%Y A057277 Column sums give A350907.
%Y A057277 The labeled version is A057274.
%Y A057277 Cf. A057270, A057276, A057278, A057279, A350794, A350797.
%K A057277 nonn,tabf
%O A057277 1,7
%A A057277 _Vladeta Jovovic_, Goran Kilibarda, Sep 14 2000
%E A057277 Terms a(46) and beyond from _Andrew Howroyd_, Jan 21 2022