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 A325476 Number of connected regular loopless multigraphs on n unlabeled nodes of degree less than n. 1
 1, 1, 1, 1, 3, 7, 75, 984, 105831, 35494648, 53493557150, 250087643676776, 4520743153498327817, 272584534800111470995411 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS Multigraphs are loopless. Initial terms computed using nauty and traces. LINKS Brendan McKay and Adolfo Piperno, Nauty and Traces FORMULA a(n) = Sum_{k=0..n-1} A328682(n, k). - Andrew Howroyd, Mar 18 2020 EXAMPLE There is no such thing as a graph with nodes of negative degree, and the "nodeless" graph has, according to the definition in the name, zero nodes of degree less than 0. So a(0) = 1. PROG (bash+nauty) for ((n=2; n<9; n++)); do a=0 for ((d=0; d<\${n}; d++)); do s=\$(geng -c -d1 \${n} -q | multig -r\${d} -u 2>&1 | cut -d ' ' -f 7 | grep -v '^\$') a=\$((a+s)) done echo \${a} done # Andrey Zabolotskiy, Sep 26 2019 CROSSREFS Cf. A289988, A289986, A319896, A319897, A324218, A325474, A328682. Sequence in context: A191485 A119572 A172995 * A234536 A103737 A354480 Adjacent sequences: A325473 A325474 A325475 * A325477 A325478 A325479 KEYWORD nonn,more,hard AUTHOR Natan Arie Consigli, May 02 2019 EXTENSIONS a(10)-a(13) from Andrew Howroyd, Mar 18 2020 STATUS approved

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Last modified February 6 01:28 EST 2023. Contains 360091 sequences. (Running on oeis4.)