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A152172
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a(n) is the number of Dyck paths of length n without height of peaks 0 (mod 3) and height of valleys 1 (mod 3)
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0
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1, 1, 2, 3, 6, 12, 26, 59, 138, 332, 814, 2028, 5118, 13054, 33598, 87143, 227542, 597640, 1577866, 4185108, 11146570, 29798682, 79932298, 215072896, 580327122, 1569942098, 4257254850, 11569980794, 31508150890, 85968266198, 234975421554
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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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+x-2*x^2-sqrt(1-2*x-3*x^2+4*x^4))/(2(1-x)x) ;
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CROSSREFS
| Cf. A086625. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Dec 03 2008]
Sequence in context: A166296 A151527 A086625 * A001677 A024422 A186771
Adjacent sequences: A152169 A152170 A152171 * A152173 A152174 A152175
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KEYWORD
| nonn
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AUTHOR
| Jun Ma (majun(AT)math.sinica.edu.tw), Nov 27 2008
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