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A000555
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Number of labeled trees of diameter 4 with n nodes.
(Formerly M5319 N2312)
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0
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60, 720, 6090, 47040, 363384, 2913120, 24560910, 218386080, 2044958916, 20112075984, 207161237010, 2228884869120, 24989300398320, 291322535242176, 3524580157816854, 44176838981652000, 572725044049055100, 7668896804089696560, 105920137922879314650, 1507138839384235136640, 22068265782102952223400, 332178010291171425732000, 5135009134117954527323550, 81449458937043220255508640
(list; graph; refs; listen; history; internal format)
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OFFSET
| 5,1
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REFERENCES
| J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Index entries for sequences related to trees
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FORMULA
| a(n)=A000551(n)-n*(n-1)*(2^(n-2)-1)
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CROSSREFS
| Sequence in context: A099344 A088945 A136008 * A034865 A138409 A024016
Adjacent sequences: A000552 A000553 A000554 * A000556 A000557 A000558
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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 and formula from Sean A. Irvine (sairvin(AT)xtra.co.nz), Nov 22 2010
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