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A000550
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Number of trees of diameter 7.
(Formerly M2969 N1201)
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0
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1, 3, 14, 42, 128, 334, 850, 2010, 4625, 10201, 21990, 46108, 94912, 191562, 380933, 746338, 1444676, 2763931, 5235309, 9822686, 18275648, 33734658, 61826344, 112550305, 203627610, 366267931, 655261559, 1166312530, 2066048261, 3643352362, 6397485909, 11188129665, 19491131627, 33831897511, 58519577756, 100885389220, 173368983090, 297021470421, 507378371670, 864277569606, 1468245046383, 2487774321958, 4204663810414, 7089200255686, 11924621337321, 20012746962064, 33513139512868, 56001473574091, 93387290773141, 155419866337746
(list; graph; refs; listen; history; internal format)
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OFFSET
| 8,2
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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
| G.f.: a(x)=(r(x)^2+r(x^2))/2, where r(x) is the generating function of A000235.
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CROSSREFS
| Sequence in context: A196236 A104905 A055650 * A124650 A063903 A115005
Adjacent sequences: A000547 A000548 A000549 * A000551 A000552 A000553
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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 generating function from Sean A. Irvine (sairvin(AT)xtra.co.nz), Nov 21 2010
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