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A243753 Number A(n,k) of Dyck paths of semilength n avoiding the consecutive step pattern given by the binary expansion of k, where 1=U=(1,1) and 0=D=(1,-1); square array A(n,k), n>=0, k>=0, read by antidiagonals. 24
1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 2, 1, 1, 0, 0, 0, 1, 1, 2, 1, 4, 1, 1, 0, 0, 0, 1, 1, 2, 4, 1, 9, 1, 1, 0, 0, 0, 1, 1, 2, 4, 9, 1, 21, 1, 1, 0, 0, 0, 1, 1, 1, 4, 9, 21, 1, 51, 1, 1, 0, 0, 0 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
0,40
LINKS
EXAMPLE
Square array A(n,k) begins:
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...
0, 0, 0, 1, 1, 1, 1, 1, 1, 1, ...
0, 0, 0, 1, 1, 1, 1, 2, 2, 2, ...
0, 0, 0, 1, 1, 2, 1, 4, 4, 4, ...
0, 0, 0, 1, 1, 4, 1, 9, 9, 9, ...
0, 0, 0, 1, 1, 9, 1, 21, 21, 23, ...
0, 0, 0, 1, 1, 21, 1, 51, 51, 63, ...
0, 0, 0, 1, 1, 51, 1, 127, 127, 178, ...
0, 0, 0, 1, 1, 127, 1, 323, 323, 514, ...
0, 0, 0, 1, 1, 323, 1, 835, 835, 1515, ...
MAPLE
A:= proc(n, k) option remember; local b, m, r, h;
if k<2 then return `if`(n=0, 1, 0) fi;
m:= iquo(k, 2, 'r'); h:= 2^ilog2(k); b:=
proc(x, y, t) option remember; `if`(y<0 or y>x, 0, `if`(x=0, 1,
`if`(t=m and r=1, 0, b(x-1, y+1, irem(2*t+1, h)))+
`if`(t=m and r=0, 0, b(x-1, y-1, irem(2*t, h)))))
end; forget(b);
b(2*n, 0, 0)
end:
seq(seq(A(n, d-n), n=0..d), d=0..14);
MATHEMATICA
A[n_, k_] := A[n, k] = Module[{b, m, r, h}, If[k<2, Return[If[n == 0, 1, 0]]]; {m, r} = QuotientRemainder[k, 2]; h = 2^Floor[Log[2, k]]; b[x_, y_, t_] := b[x, y, t] = If[y<0 || y>x, 0, If[x == 0, 1, If[t == m && r == 1, 0, b[x-1, y+1, Mod[2*t+1, h]]] + If[t == m && r == 0, 0, b[x-1, y-1, Mod[2*t, h]]]]]; b[2*n, 0, 0]]; Table[ Table[A[n, d-n], {n, 0, d}], {d, 0, 14}] // Flatten (* Jean-François Alcover, Jan 27 2015, after Alois P. Heinz *)
CROSSREFS
Columns give: 0, 1, 2: A000007, 3, 4, 6: A000012, 5: A001006(n-1) for n>0, 7, 8, 14: A001006, 9: A135307, 10: A078481 for n>0, 11, 13: A105633(n-1) for n>0, 12: A082582, 15, 16: A036765, 19, 27: A114465, 20, 24, 26: A157003, 21: A247333, 25: A187256(n-1) for n>0.
Main diagonal gives A243754 or column k=0 of A243752.
Sequence in context: A354841 A339772 A250211 * A219238 A025918 A030425
KEYWORD
nonn,tabl
AUTHOR
Alois P. Heinz, Jun 09 2014
STATUS
approved

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Last modified May 27 02:41 EDT 2024. Contains 372847 sequences. (Running on oeis4.)