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A339160 Triangle read by rows: T(n,k) is the number of unlabeled nonseparable (or 2-connected) loopless multigraphs with n edges and k nodes (n >= 1, 2 <= k <= n + 1). 6
1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 2, 2, 1, 0, 1, 3, 6, 3, 1, 0, 1, 4, 11, 11, 4, 1, 0, 1, 5, 22, 33, 23, 5, 1, 0, 1, 7, 38, 89, 96, 40, 7, 1, 0, 1, 8, 63, 212, 345, 234, 70, 8, 1, 0, 1, 10, 98, 463, 1083, 1146, 546, 110, 10, 1, 0, 1, 12, 151, 943, 3068, 4739, 3505, 1169, 176, 12, 1, 0 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
1,12
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..210 (rows 1..20)
FORMULA
T(n,2) = T(n,n) = 1.
EXAMPLE
Triangle T(n,k) begins (n edges >= 1, k vertices >= 2):
1;
1, 0;
1, 1, 0;
1, 1, 1, 0;
1, 2, 2, 1, 0;
1, 3, 6, 3, 1, 0;
1, 4, 11, 11, 4, 1, 0;
1, 5, 22, 33, 23, 5, 1, 0;
1, 7, 38, 89, 96, 40, 7, 1, 0;
1, 8, 63, 212, 345, 234, 70, 8, 1, 0;
1, 10, 98, 463, 1083, 1146, 546, 110, 10, 1, 0;
1, 12, 151, 943, 3068, 4739, 3505, 1169, 176, 12, 1, 0;
...
CROSSREFS
Column k=3 is A001399(n-3).
Row sums are A010357.
Sequence in context: A351995 A055290 A125629 * A355755 A141335 A133624
KEYWORD
nonn,tabl
AUTHOR
Andrew Howroyd, Dec 05 2020
STATUS
approved

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Last modified July 18 21:02 EDT 2024. Contains 374388 sequences. (Running on oeis4.)