A308522 Maximum number of simple graphs with no isolated vertices on n nodes with identical degree sequences.

1, 1, 1, 2, 5, 20, 184, 3020, 65500

Offset

2,4

Links

Table of n, a(n) for n=2..10.

Peter Adams, Roger B. Eggleton, and James A. MacDougall, Taxonomy of Graphs of Order 10, Congressus Numerantium, 180 (2006), 65.

Peter Adams, Roger B. Eggleton, and James A. MacDougall, Taxonomy of Graphs of Order 10, Web page.

Prog

(Sage)
def max_graphs(n):
    if n > 1:
        count = defaultdict(int)
        sequences = [tuple(graph.degree_sequence()) for graph in graphs(n) if graph and not 0 in graph.degree_sequence()]
        for seq in sequences:
            count[seq] += 1
        max_cnt = max(count.values())
    else:
        return None
    return max_cnt

Crossrefs

Sequence in context: A005331 A261005 A158872 * A216462 A006893 A003163

Adjacent sequences: A308519 A308520 A308521 * A308523 A308524 A308525

Keyword

nonn,hard,more

Author

Sharat Chandra, Jun 04 2019

Status

approved