This site is supported by donations to The OEIS Foundation. Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A247298 Number of weighted lattice paths B(n) having no uudd strings. 1
 1, 1, 2, 4, 8, 17, 36, 80, 180, 410, 946, 2203, 5173, 12233, 29108, 69643, 167437, 404311, 980125, 2384441, 5819576, 14245384, 34964611, 86032272, 212172668, 524371704, 1298509438, 3221425567, 8005623916, 19926840746, 49674610998, 124006308008 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS B(n) is the set of lattice paths of weight n that start in (0,0), end on the horizontal axis and never go below this axis, whose steps are of the following four kinds: h = (1,0) of weight 1, H = (1,0) of weight 2, u = (1,1) of weight 2, and d = (1,-1) of weight 1. The weight of a path is the sum of the weights of its steps. a(n) = A247297(n,0). LINKS M. Bona and A. Knopfmacher, On the probability that certain compositions have the same number of parts, Ann. Comb., 14 (2010), 291-306. FORMULA G.f. G = G(z) satisfies G = 1 + z*G + z^2*G + z^3*G*(G -  z^3 ). EXAMPLE a(6)=36 because among the 37 (=A004148(7)) paths in B(6) only uudd contains uudd. MAPLE eq := G = 1+z*G+z^2*G+z^3*G*(G-z^3): G := RootOf(eq, G): Gser := series(G, z = 0, 37): seq(coeff(Gser, z, n), n = 0 .. 35); CROSSREFS Cf. A004148, A247297. Sequence in context: A202844 A093951 A137255 * A325928 A076892 A106462 Adjacent sequences:  A247295 A247296 A247297 * A247299 A247300 A247301 KEYWORD nonn AUTHOR Emeric Deutsch, Sep 17 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 18 20:13 EDT 2019. Contains 327181 sequences. (Running on oeis4.)