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A034799
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Triangle read by rows: T(n,k) is the number of partially labeled trees with n nodes, k of which are labeled, 0 <= k <= n.
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9
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1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 2, 4, 9, 16, 16, 3, 9, 26, 67, 125, 125, 6, 20, 75, 251, 680, 1296, 1296, 11, 48, 214, 888, 3135, 8716, 16807, 16807, 23, 115, 612, 3023, 13155, 47787, 134960, 262144, 262144, 47, 286, 1747, 10038, 51873, 232154, 858578, 2450309, 4782969, 4782969
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refs;
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history;
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OFFSET
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0,8
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REFERENCES
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J. Riordan, An Introduction to Combinatorial Analysis, p. 138.
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LINKS
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FORMULA
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Reference gives generating function.
E.g.f.: r(x,y) - (1/2)*r(x,y)^2 + (1/2)*r(x^2) where r(x,y) is the e.g.f. for A008295 and r(x) is the o.g.f. for A000081. - Sean A. Irvine, Sep 04 2020
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EXAMPLE
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Triangle begins:
1;
1, 1;
1, 1, 1;
1, 2, 3, 3;
2, 4, 9, 16, 16;
...
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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