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A122086
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Number of unlabeled free bicolored trees with n nodes (the colors are not interchangeable).
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2
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2, 1, 2, 3, 6, 10, 22, 42, 94, 203, 470, 1082, 2602, 6270, 15482, 38525, 97258, 247448, 635910, 1645411, 4289010, 11245670, 29656148, 78595028, 209273780, 559574414, 1502130920, 4046853091, 10939133170, 29661655793
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Row sums of A122085.
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REFERENCES
| R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1978.
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FORMULA
| For n even, a(n) = 2*A000055(n) - A000081(n/2), for n odd, a(n) = 2*A000055(n).
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CROSSREFS
| Cf. A122085. Same as A125702 except for n = 1.
Sequence in context: A056493 A001371 A001037 * A082594 A051850 A077013
Adjacent sequences: A122083 A122084 A122085 * A122087 A122088 A122089
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Oct 19 2006
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EXTENSIONS
| Edited by Christian Bower (bowerc(AT)usa.net) and Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Jan 05 2007
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