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A046647
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Number of certain rooted planar maps.
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2
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1, 6, 26, 120, 594, 3094, 16728, 93024, 528770, 3058770, 17948970, 106585440, 639318456, 3867821640, 23574446992, 144621823632, 892293152994, 5533289372170, 34468829508750, 215594574231960, 1353464311979010
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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REFERENCES
| W. G. Brown, Enumeration of non-separable planar maps, Canad. J. Math., 15 (1963), 526-545.
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FORMULA
| a(2)=1; a(n)=4(7n-15)(3n-6)!/[(n-2)!(2n-2)! ] - Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 03 2004
G.f.: (g+1)*(3*g+1)/(g-1)^2 where g*(1-g)^2 = x. - Mark van Hoeij, Nov 10 2011
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CROSSREFS
| A diagonal of A046651. Cf. A046646.
Sequence in context: A145374 A124465 A164549 * A046233 A140231 A144037
Adjacent sequences: A046644 A046645 A046646 * A046648 A046649 A046650
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 03 2004
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