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A005751
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Number of matched trees with n nodes.
(Formerly M1478)
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1
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1, 1, 2, 5, 15, 49, 180, 701, 2891, 12371, 54564, 246319, 1133602, 5300255, 25119554, 120441076, 583373822, 2851023191, 14044428996, 69677569603, 347904448580, 1747195558582, 8820848574074, 44747514381341, 228004950808983
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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REFERENCES
| R. Simion, Trees with 1-factors and oriented trees, Discrete Math., 88 (1991), 93-104.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Alois P. Heinz, Table of n, a(n) for n = 1..400
Index entries for sequences related to trees
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MAPLE
| with(numtheory): r2:= proc(n) option remember; local m; `if` (n=1, 1, 2/(n-1) *add (r2(m) *add (d*r2(d), d=divisors(n-m)), m=1..n-1)) end: p2:= proc(n) option remember; local m; `if` (n=1, 1, 1/(n-1) *add (p2(m) *add (d*r2(d), d=divisors(n-m)), m=1..n-1)) end: m2:= n-> (r2(n) -add (r2(m) *r2(n-m), m=1..n-1) +`if` (irem(n, 2)=0, r2(n/2), p2((n+1)/2)))/2: seq (m2(n), n=1..30); # Alois P. Heinz, Aug 04 2009
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CROSSREFS
| Sequence in context: A079146 A000734 A148366 * A202182 A149944 A149945
Adjacent sequences: A005748 A005749 A005750 * A005752 A005753 A005754
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 04 2009
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