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A368569
Irregular triangle read by rows: T(n,k) is the number of essential graphs with n nodes and k (directed or undirected) edges (n >= 1, 0 <= k <= n*(n-1)/2).
1
1, 1, 1, 1, 3, 6, 1, 1, 6, 27, 60, 66, 24, 1, 1, 10, 75, 350, 1120, 2130, 2595, 1730, 690, 80, 1, 1, 15, 165, 1235, 6930, 27882, 79825, 162315, 236490, 245150, 180936, 91560, 29890, 5190, 240, 1
OFFSET
1,5
EXAMPLE
Triangle T(n,k) (with n >= 1 and 0 <= k <= n*(n-1)/2) begins as follows:
1;
1, 1;
1, 3, 6, 1;
1, 6, 27, 60, 66, 24, 1;
1, 10, 75, 350, 1120, 2130, 2595, 1730, 690, 80, 1;
...
CROSSREFS
Row sums give A007984.
Row lengths give A000124.
Column k=1 is A000217.
Column k=2 is A239568.
Sequence in context: A104611 A076790 A095693 * A032660 A102257 A347196
KEYWORD
nonn,tabf,more
AUTHOR
Moritz Schauer, Feb 06 2024
STATUS
approved