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A263853
Number of 3-ascent sequences of length n with no consecutive repeated letters.
2
1, 1, 3, 12, 54, 276, 1574, 9916, 68394, 512671, 4150148, 36086135, 335447341, 3319876281, 34853551700, 386889999296, 4527701024471, 55715658165361, 719205555167707, 9717733698168073, 137168409543673446, 2018981393006166050, 30936712227446490134
OFFSET
0,3
LINKS
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+3))
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 + 3}]]; 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=3 of A264909.
Sequence in context: A193115 A270489 A335819 * A266083 A245374 A052673
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 18 2015
EXTENSIONS
a(10)-a(22) from Alois P. Heinz, Nov 19 2015
STATUS
approved