A288113 Number of Dyck paths of semilength n such that each level has exactly six peaks or no peaks.

1, 0, 0, 0, 0, 0, 1, 1, 6, 16, 31, 56, 102, 179, 426, 1490, 5164, 18715, 73281, 253183, 741420, 1915072, 4599352, 10845192, 26990806, 76446936, 251549461, 918616924, 3497341145, 13161267180, 47114251055, 157204766841, 487208649994, 1416324380706, 3944267803650

Offset: 0

Author

Alois P. Heinz, Jun 05 2017

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..1000
• Wikipedia, Counting lattice paths

Crossrefs

Column k=6 of A288108.

Programs

Maple

b:= proc(n, k, j) option remember; `if`(n=j, 1, add(
      b(n-j, k, i)*(binomial(j-1, i-1)+binomial(i, k)
       *binomial(j-1, i-1-k)), i=1..min(j+k, n-j)))
    end:
a:= n-> `if`(n=0, 1, b(n, 6$2)):
seq(a(n), n=0..40);

Mathematica

b[n_, k_, j_] := b[n, k, j] = If[n == j, 1, Sum[b[n - j, k, i]*(Binomial[j - 1, i - 1] + Binomial[i, k]*Binomial[j - 1, i - 1 - k]), {i, 1, Min[j + k, n - j]}]];
a[n_] := If[n == 0, 1, b[n, 6, 6]];
Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Jun 02 2018, from Maple *)