A263854 Number of 4-ascent sequences of length n with no consecutive repeated letters.

1, 1, 4, 20, 110, 670, 4470, 32440, 254490, 2146525, 19374399, 186356108, 1903188611, 20569046543, 234562076984, 2814847291152, 35461339995304, 467952904377739, 6455368497736153, 92919917495585794, 1393239845937756837, 21726457354762648604

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..200

S. Kitaev, J. Remmel, p-Ascent Sequences, arXiv preprint arXiv:1503.00914 [math.CO], 2015.

Maple

b:= proc(n, i, t) option remember; `if`(n<1, 1, add(
      `if`(j=i, 0, b(n-1, j, t+`if`(j>i, 1, 0))), j=0..t+4))
    end:
a:= n-> b(n-1, 0$2):
seq(a(n), n=0..30);  # Alois P. Heinz, Nov 19 2015

Mathematica

b[n_, i_, t_] := b[n, i, t] = If[n < 1, 1, Sum[If[j == i, 0, b[n - 1, j, t + If[j > i, 1, 0]]], {j, 0, t + 4}]]; a[n_] := b[n - 1, 0, 0]; Table[ a[n], {n, 0, 30}] (* Jean-François Alcover, Feb 17 2016, after Alois P. Heinz *)

Crossrefs

Column k=4 of A264909.

Sequence in context: A153295 A006770 A158827 * A026156 A025183 A014523

Adjacent sequences: A263851 A263852 A263853 * A263855 A263856 A263857

Keyword

nonn

Author

N. J. A. Sloane, Nov 18 2015

Extensions

a(10)-a(21) from Alois P. Heinz, Nov 19 2015

Status

approved