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A333158
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Irregular triangle read by rows: T(n,k) is the number of k-regular graphs on n labeled nodes with loops allowed, n >= 1, 0 <= k <= n + 1.
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2
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1, 0, 1, 1, 1, 1, 1, 1, 0, 2, 0, 1, 1, 3, 8, 8, 3, 1, 1, 0, 38, 0, 38, 0, 1, 1, 15, 208, 730, 730, 208, 15, 1, 1, 0, 1348, 0, 20670, 0, 1348, 0, 1, 1, 105, 10126, 188790, 781578, 781578, 188790, 10126, 105, 1, 1, 0, 86174, 0, 37885204, 0, 37885204, 0, 86174, 0, 1
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OFFSET
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1,10
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COMMENTS
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A loop adds 2 to the degree of its vertex.
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LINKS
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FORMULA
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T(n,k) = T(n, n+1-k).
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EXAMPLE
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Triangle begins:
1, 0, 1;
1, 1, 1, 1;
1, 0, 2, 0, 1;
1, 3, 8, 8, 3, 1;
1, 0, 38, 0, 38, 0, 1;
1, 15, 208, 730, 730, 208, 15, 1;
1, 0, 1348, 0, 20670, 0, 1348, 0, 1;
1, 105, 10126, 188790, 781578, 781578, 188790, 10126, 105, 1;
...
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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