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A152225
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Number of Dyck paths of semilength n with no peaks at height 0 (mod 3) and no valleys at height 2 (mod 3).
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0
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1, 1, 2, 4, 9, 22, 56, 146, 388, 1048, 2869, 7942, 22192, 62510, 177308, 506008, 1451866, 4185788, 12119696, 35227748, 102753800, 300672368, 882373261, 2596389190, 7658677856, 22642421206, 67081765932, 199128719896
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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REFERENCES
| Shu-Chung Liu, Jun Ma and Yeong-Nan Yeh, "Dyck Paths with Peak- and Valley-Avoiding Sets", Stud. Appl Math. 121 (3) (2008) 263-289
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FORMULA
| gf := (1-2*x+2*x^2-sqrt(1-4*x+4*x^2-4*x^3))/(2x^2) ;
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CROSSREFS
| Cf. A091561, A025265, A025247. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Dec 03 2008]
Sequence in context: A107092 A055588 A088456 * A091561 A025265 A037245
Adjacent sequences: A152222 A152223 A152224 * A152226 A152227 A152228
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KEYWORD
| nonn
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AUTHOR
| Majun (majun(AT)math.sinica.edu.tw), Nov 29 2008
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EXTENSIONS
| Edited by Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 20 2008
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