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 A191310 Triangle read by rows: T(n,k) is the number of dispersed Dyck paths (i.e., Motzkin paths with no (1,0) steps at positive heights) of length n having k up-steps starting at level 0. 1

%I #15 Jul 17 2017 02:18:06

%S 1,1,1,1,1,2,1,4,1,1,6,3,1,10,8,1,1,14,16,4,1,23,32,13,1,1,32,56,32,5,

%T 1,55,102,74,19,1,1,78,170,152,55,6,1,143,302,307,144,26,1,1,208,498,

%U 580,336,86,7,1,405,890,1102,748,251,34,1,1,602,1478,2004,1564,652,126,8,1,1228,2691,3714,3200,1587,405,43,1

%N Triangle read by rows: T(n,k) is the number of dispersed Dyck paths (i.e., Motzkin paths with no (1,0) steps at positive heights) of length n having k up-steps starting at level 0.

%C Row n has 1 + floor(n/2) entries.

%C Sum of entries in row n is binomial(n, floor(n/2)) = A001405(n).

%C Sum_{k>=0} k*T(n,k) = A093387(n+1).

%F G.f.: G(t,z) = 2/(2-2*z-t*(1-sqrt(1-4*z^2))).

%e T(5,2)=3 because we have HUDUD, UDHUD, and UDUDH, where U=(1,1), D=(1,-1), H=(1,0).

%e Triangle starts:

%e 1;

%e 1;

%e 1, 1;

%e 1, 2;

%e 1, 4, 1;

%e 1, 6, 3;

%e 1, 10, 8, 1;

%e 1, 14, 16, 4;

%e 1, 23, 32, 13, 1;

%p G := 2/(2-2*z-t*(1-sqrt(1-4*z^2))): Gser := simplify(series(G, z = 0, 20)): for n from 0 to 16 do P[n] := sort(coeff(Gser, z, n)) end do: for n from 0 to 16 do seq(coeff(P[n], t, k), k = 0 .. floor((1/2)*n)) end do; # yields sequence in triangular form

%Y Cf. A001405, A093387.

%K nonn,tabf

%O 0,6

%A _Emeric Deutsch_, May 30 2011

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Last modified June 9 09:47 EDT 2023. Contains 363177 sequences. (Running on oeis4.)