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A275784 Number A(n,k) of up-down sequences with k copies each of 1,2,...,n; square array A(n,k), n>=0, k>=0, read by antidiagonals. 7
1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 2, 1, 1, 0, 1, 4, 5, 1, 1, 0, 1, 12, 53, 16, 1, 1, 0, 1, 36, 761, 936, 61, 1, 1, 0, 1, 120, 12661, 87336, 25325, 272, 1, 1, 0, 1, 400, 229705, 9929000, 18528505, 933980, 1385, 1, 1, 0, 1, 1400, 4410665, 1267945800, 17504311533, 6376563600, 45504649, 7936, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,14

LINKS

Alois P. Heinz, Antidiagonals n = 0..15, flattened

EXAMPLE

A(4,1) = 5: 1324, 1423, 2314, 2413, 3412.

A(3,2) = 4: 121323, 132312, 231213, 231312.

A(3,3) = 12: 121313232, 121323132, 121323231, 131213232, 132312132, 132323121, 231213132, 231213231, 231312132, 231323121, 232312131, 232313121.

A(2,4) = 1: 12121212.

Square array A(n,k) begins:

1,   1,      1,          1,              1,              1, ...

1,   1,      0,          0,              0,              0, ...

1,   1,      1,          1,              1,              1, ...

1,   2,      4,         12,             36,            120, ...

1,   5,     53,        761,          12661,         229705, ...

1,  16,    936,      87336,        9929000,     1267945800, ...

1,  61,  25325,   18528505,    17504311533, 19126165462061, ...

1, 272, 933980, 6376563600, 59163289699260, ...

MAPLE

b:= proc(n, l) option remember; `if`(l=[], 1, `if`(irem(add(i,

      i=l), 2)=0, add(b(i, subsop(i=`if`(l[i]=1, [][], l[i]-1),

      l)), i=n+1..nops(l)), add(b(i-`if`(l[i]=1, 1, 0), subsop(

      i=`if`(l[i]=1, [][], l[i]-1), l)), i=1..n-1)))

    end:

A:= (n, k)->`if`(k=0, 1, b(`if`(irem(k*n, 2)=0, 0, n+1), [k$n])):

seq(seq(A(n, d-n), n=0..d), d=0..10);

MATHEMATICA

b[n_, l_List] := b[n, l] = If[l == {}, 1, If[EvenQ[Total[l]], Sum[b[i, ReplacePart[l, i -> If[l[[i]] == 1, Nothing, l[[i]]-1]]], {i, n+1, Length[l]}], Sum[b[i - If[l[[i]] == 1, 1, 0], ReplacePart[l, i -> If[l[[i]] == 1, Nothing, l[[i]]-1]]], {i, 1, n-1}]]]; A[n_, k_] := If[k == 0, 1, b[If[EvenQ[k*n], 0, n+1], Array[k&, n]]]; Table[A[n, d-n], {d, 0, 10}, {n, 0, d}] // Flatten (* Jean-Fran├žois Alcover, Jan 23 2017, adapted from Maple *)

CROSSREFS

Columns k=0-3 give: A000012, A000111, A275801, A276636.

Rows n=2-5 give: A000012, A241530, A036916, A276637.

Cf. A269129.

Sequence in context: A108934 A108947 A152459 * A097608 A168261 A180997

Adjacent sequences:  A275781 A275782 A275783 * A275785 A275786 A275787

KEYWORD

nonn,tabl

AUTHOR

Alois P. Heinz, Aug 12 2016

STATUS

approved

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Last modified October 17 19:36 EDT 2018. Contains 316293 sequences. (Running on oeis4.)