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A005755
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Number of identity matched trees with n nodes.
(Formerly M3517)
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1
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0, 0, 0, 1, 4, 16, 64, 252, 1018, 4182, 17510, 74510, 322034, 1410362, 6251114, 27998532, 126583634, 577079333, 2650573354, 12256481666, 57021299394, 266754944481, 1254245360430, 5924659521632, 28105641930102, 133853504339029, 639801068848128
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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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..450
Index entries for sequences related to trees
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MAPLE
| with(numtheory): b2:= proc(n) option remember; local m; `if` (n=1, 1, 2/(n-1) *add (b2(m) *add((-1)^((n-m)/d+1) *d*b2(d), d=divisors(n-m)), m=1..n-1)) end: c2:= proc(n) option remember; local m; `if` (n=1, 1, 1/(n-1) *add (c2(m) *add((-1)^((n-m)/d+1) *d*b2(d), d=divisors(n-m)), m=1..n-1)) end: a2:= n-> (b2(n) -add (b2(m) *b2(n-m), m=1..n-1) -`if` (irem(n, 2)=0, b2(n/2), c2((n+1)/2)))/2: seq (a2(n), n=1..30); # Alois P. Heinz, Aug 04 2009
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CROSSREFS
| Sequence in context: A180239 A006811 A188714 * A077821 A206450 A000302
Adjacent sequences: A005752 A005753 A005754 * A005756 A005757 A005758
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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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