A057277 Triangle T(n,k) of number of digraphs with a source on n unlabeled nodes with k arcs, k=0..n*(n-1).
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, 229, 573, 1058, 1448, 1653, 1487, 1153, 707, 379, 154, 61, 16, 5, 1, 1, 0, 0, 0, 0, 0, 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
Offset: 1
Examples
Triangle begins: [1], [0, 1, 1], [0, 0, 2, 4, 4, 1, 1], [0, 0, 0, 4, 16, 34, 46, 38, 27, 13, 5, 1, 1], .... The number of digraphs with a source on 3 unlabeled nodes is 12 = 2+4+4+1+1.
Links
- Andrew Howroyd, Table of n, a(n) for n = 1..2680 (rows 1..20)
Crossrefs
Programs
-
PARI
\\ See PARI link in A350794 for program code. { my(A=A057277triang(5)); for(n=1, #A, print(A[n])) } \\ Andrew Howroyd, Jan 21 2022
Extensions
Terms a(46) and beyond from Andrew Howroyd, Jan 21 2022