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Search: id:A122193
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| A122193 |
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Triangle T(n,k) of number of graphs with n labeled vertices and k labeled edges and without isolated vertices, n = 1,.., k = 2..2*n. |
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+0
2
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| 1, 1, 6, 6, 1, 24, 114, 180, 90, 1, 78, 978, 4320, 8460, 7560, 2520, 1, 240, 6810, 63540, 271170, 604800, 730800, 453600, 113400, 1, 726, 43746, 774000, 6075900, 25424280, 61923960, 90720000, 78813000, 37422000, 7484400
(list; table; graph; listen)
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OFFSET
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2,3
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FORMULA
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E.g.f.: exp(-x)*Sum(exp(binomial(n,2)*y)*x^n/n!,n=0..infinity). Row sums give A055203.
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EXAMPLE
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1; 1,6,6; 1,24,114,180,90; 1,78,978,4320,8460,7560,2520; ...
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CROSSREFS
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Sequence in context: A105817 A093313 A098267 this_sequence A098369 A078740 A021155
Adjacent sequences: A122190 A122191 A122192 this_sequence A122194 A122195 A122196
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KEYWORD
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easy,nonn,tabl
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AUTHOR
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Vladeta Jovovic (vladeta(AT)eunet.rs), Aug 24 2006
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