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A288682 Number of Dyck paths of semilength n such that no positive level has fewer than six peaks.

%I A288682 #13 Apr 24 2021 08:44:52
%S A288682 1,0,0,0,0,0,1,1,1,1,1,1,1,8,156,1213,5232,16091,41834,100320,229851,
%T A288682 513699,1166304,3068322,11294356,54431307,271824026,1253186445,
%U A288682 5233138157,20031588131,71538367677,242280234545,789260222205,2507719402158,7900354628357
%N A288682 Number of Dyck paths of semilength n such that no positive level has fewer than six peaks.
%H A288682 Alois P. Heinz, <a href="/A288682/b288682.txt">Table of n, a(n) for n = 0..300</a>
%H A288682 Wikipedia, <a href="https://en.wikipedia.org/wiki/Lattice_path#Counting_lattice_paths">Counting lattice paths</a>
%t A288682 b[n_, k_, j_]:=b[n, k, j]=If[j==n, 1, Sum[Sum[Binomial[i, m] Binomial[j - 1, i - 1 - m], {m, Max[k, i - j], i - 1}] b[n - j, k, i], {i, n - j}]];  a[n_]:=If[n==0, 1, Sum[b[n, 6, j], {j, 6, n}]]; Table[a[n], {n, 0, 35}] (* _Indranil Ghosh_, Aug 10 2017 *)
%o A288682 (Python)
%o A288682 from sympy.core.cache import cacheit
%o A288682 from sympy import binomial
%o A288682 @cacheit
%o A288682 def b(n, k, j): return 1 if j==n else sum([sum([binomial(i, m)*binomial(j - 1, i - 1 - m) for m in range(max(k, i - j), i)])*b(n - j, k, i) for i in range(1, n - j + 1)])
%o A288682 def a(n): return 1 if n==0 else sum([b(n, 6, j) for j in range(6, n + 1)])
%o A288682 print([a(n) for n in range(36)]) # _Indranil Ghosh_, Aug 10 2017
%Y A288682 Column k=6 of A288386.
%Y A288682 Cf. A000108.
%K A288682 nonn
%O A288682 0,14
%A A288682 _Alois P. Heinz_, Jun 13 2017