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A186715
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Irregular triangle C(n,k)=number of connected k-regular graphs on n vertices having girth at least five.
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15
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1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 2, 0, 0, 1, 0, 0, 0, 1, 9, 0, 0, 1, 0, 0, 0, 1, 49, 0, 0, 1, 0, 0, 0, 1, 455, 0, 0, 1, 0, 1, 0, 0, 1, 5783, 2, 0, 0, 1, 0, 8, 0, 0, 1, 90938, 131, 0, 0, 1, 0, 3917, 0, 0, 1, 1620479, 123859
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OFFSET
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1,34
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COMMENTS
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Brendan McKay has observed that C(26,3) = 31478584 is output by genreg, minibaum, and snarkhunter, but Meringer's table currently has C(26,3) = 31478582. - Jason Kimberley, May 19 2017
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LINKS
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EXAMPLE
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01: 1;
02: 0, 1;
03: 0, 0;
04: 0, 0;
05: 0, 0, 1;
06: 0, 0, 1;
07: 0, 0, 1;
08: 0, 0, 1;
09: 0, 0, 1;
10: 0, 0, 1, 1;
11: 0, 0, 1, 0;
12: 0, 0, 1, 2;
13: 0, 0, 1, 0;
14: 0, 0, 1, 9;
15: 0, 0, 1, 0;
16: 0, 0, 1, 49;
17: 0, 0, 1, 0;
18: 0, 0, 1, 455;
19: 0, 0, 1, 0, 1;
20: 0, 0, 1, 5783, 2;
21: 0, 0, 1, 0, 8;
22: 0, 0, 1, 90938, 131;
23: 0, 0, 1, 0, 3917;
24: 0, 0, 1, 1620479, 123859;
25: 0, 0, 1, 0, 4131991;
26: 0, 0, 1, 31478584, 132160608;
27: 0, 0, 1, 0, 4018022149;
28: 0, 0, 1, 656783890, 118369811960;
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CROSSREFS
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Triangular arrays C(n,k) counting connected simple k-regular graphs on n vertices with girth at least g: A068934 (g=3), A186714 (g=4), this sequence (g=5), A186716 (g=6), A186717 (g=7), A186718 (g=8), A186719 (g=9).
Triangular arrays C(n,k) counting connected simple k-regular graphs on n vertices with girth exactly g: A186733 (g=3), A186734 (g=4).
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KEYWORD
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nonn,hard,tabf
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AUTHOR
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STATUS
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approved
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