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A288147 Number of Dyck paths of semilength n such that the number of peaks is strongly increasing from lower to higher levels and no positive level is peakless. 4
1, 1, 1, 1, 3, 6, 12, 31, 68, 186, 506, 1299, 3481, 9712, 27692, 79587, 232743, 694896, 2086245, 6248158, 18771510, 57007483, 175149700, 542313513, 1688360997, 5288335561, 16679137617, 52933231538, 168768966207, 539981776609, 1733555552587, 5587076558809 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,5
LINKS
EXAMPLE
a(5) = 6:
/\ /\ /\ /\
/\/\/\/\/\ /\/ \/ \ / \/\/ \
.
/\ /\ /\/\/\ /\/\/\
/ \/ \/\ /\/ \ / \/\
MAPLE
b:= proc(n, k, j) option remember; `if`(n=j, 1, add(add(
b(n-j, t, i)*binomial(i, t)*binomial(j-1, i-1-t),
t=max(1, i-j)..min(k-1, n-j, i-1)), i=1..n-j))
end:
a:= n-> `if`(n=0, 1, add(b(n, k$2), k=1..n)):
seq(a(n), n=0..34);
MATHEMATICA
b[n_, k_, j_] := b[n, k, j] = If[n == j, 1, Sum[Sum[b[n - j, t, i]* Binomial[i, t]*Binomial[j - 1, i - 1 - t], {t, Max[1, i - j], Min[k - 1, n - j, i - 1]}], {i, 1, n - j}]];
a[n_] := If[n == 0, 1, Sum[b[n, k, k], {k, 1, n}]];
Table[a[n], {n, 0, 34}] (* Jean-François Alcover, May 29 2018, from Maple *)
CROSSREFS
Sequence in context: A049941 A219634 A252696 * A026079 A066710 A033648
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jun 05 2017
STATUS
approved

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Last modified July 20 05:10 EDT 2024. Contains 374441 sequences. (Running on oeis4.)