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A006411
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Nonseparable planar tree-rooted maps.
(Formerly M3073)
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2
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3, 20, 75, 210, 490, 1008, 1890, 3300, 5445, 8580, 13013, 19110, 27300, 38080, 52020, 69768, 92055, 119700, 153615, 194810, 244398, 303600, 373750, 456300, 552825, 665028, 794745, 943950, 1114760, 1309440
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Walsh, T. R. S.; Lehman, A. B.; Counting rooted maps by genus. III: Nonseparable maps. J. Combinatorial Theory Ser. B 18 (1975), 222-259.
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..1000
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FORMULA
| G.f.: x*(3+2*x)/(1-x)^6.
a(n) = n*(n+1)*(n+2)^2*(n+3)/24. [Bruno Berselli, May 17 2011]
a(n)=A027777(n)/2 - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 23 2007
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PROG
| (MAGMA) [n*(n+1)*(n+2)^2*(n+3)/24: n in [1..50]]; // Vincenzo Librandi, May 19 2011
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CROSSREFS
| Cf. A027777.
Sequence in context: A160456 A196741 A196899 * A129549 A171673 A185065
Adjacent sequences: A006408 A006409 A006410 * A006412 A006413 A006414
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KEYWORD
| nonn,easy,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| G.f. adapted to the offset by Bruno Berselli, May 17 2011
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