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A323224 A(n, k) = [x^k] C^n*x/(1 - x) where C = 2/(1 + sqrt(1 - 4*x)), square array read by ascending antidiagonals with n >= 0 and k >= 0. 4
0, 0, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 4, 1, 0, 1, 4, 8, 9, 1, 0, 1, 5, 13, 22, 23, 1, 0, 1, 6, 19, 41, 64, 65, 1, 0, 1, 7, 26, 67, 131, 196, 197, 1, 0, 1, 8, 34, 101, 232, 428, 625, 626, 1, 0, 1, 9, 43, 144, 376, 804, 1429, 2055, 2056, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,9

LINKS

Table of n, a(n) for n=0..65.

FORMULA

For n>0 and k>0 let X(n, k) denote the set of all tuples of length n with elements from {0, ..., k-1} with sum < k. Let C(m) denote the m-th Catalan number. Then: A(n, k) = Sum_{(j1,...,jn) in X(n, k)} C(j1)*C(j2)*...*C(jn).

A(n, k) = T(n + k, k) with T(n, k) = T(n-1, k) + T(n, k-1) with T(n, k) = 0 if n <= 0 or k < 0 and T(n, n) = 1.

EXAMPLE

The square array starts:

   [n\k]  0  1   2   3    4     5     6      7       8       9

    ---------------------------------------------------------------

    [0]   0, 1,  1,  1,   1,    1,    1,     1,      1,      1, ... A057427

    [1]   0, 1,  2,  4,   9,   23,   65,   197,    626,   2056, ... A014137

    [2]   0, 1,  3,  8,  22,   64,  196,   625,   2055,   6917, ... A014138

    [3]   0, 1,  4, 13,  41,  131,  428,  1429,   4861,  16795, ... A001453

    [4]   0, 1,  5, 19,  67,  232,  804,  2806,   9878,  35072, ... A114277

    [5]   0, 1,  6, 26, 101,  376, 1377,  5017,  18277,  66727, ... A143955

    [6]   0, 1,  7, 34, 144,  573, 2211,  8399,  31655, 118865, ...

    [7]   0, 1,  8, 43, 197,  834, 3382, 13378,  52138, 201364, ...

    [8]   0, 1,  9, 53, 261, 1171, 4979, 20483,  82499, 327656, ...

    [9]   0, 1, 10, 64, 337, 1597, 7105, 30361, 126292, 515659, ...

.

Triangle given by ascending antidiagonals:

    0;

    0, 1;

    0, 1, 1;

    0, 1, 2,  1;

    0, 1, 3,  4,   1;

    0, 1, 4,  8,   9,   1;

    0, 1, 5, 13,  22,  23,   1;

    0, 1, 6, 19,  41,  64,  65,   1;

    0, 1, 7, 26,  67, 131, 196, 197,   1;

    0, 1, 8, 34, 101, 232, 428, 625, 626, 1;

.

The difference table of a column successively gives the preceding columns, here starting with column 6.

col(6) = 1, 65, 196, 428, 804, 1377, 2211, 3382, 4979, 7105, ...

col(5) =    64, 131, 232, 376,  573,  834, 1171, 1597, 2126, ...

col(4) =         67, 101, 144,  197,  261,  337,  426,  529, ...

col(3) =              34,  43,   53,   64,   76,   89,  103, ...

col(2) =                    9,   10,   11,   12,   13,   14, ...

col(1) =                          1,    1,    1,    1,    1, ...

col(0) =                                0,    0,    0,    0, ...

.

Example for the sum formula: C(0) = 1, C(1) = 1, C(2) = 2 and C(3) = 5.

X(3, 4) = {{0,0,0}, {0,0,1}, {0,1,0}, {1,0,0}, {0,0,2}, {0,1,1}, {0,2,0}, {1,0,1},

{1,1,0}, {2,0,0}, {0,0,3}, {0,1,2}, {0,2,1}, {0,3,0}, {1,0,2}, {1,1,1}, {1,2,0},

{2,0,1}, {2,1,0}, {3,0,0}}. T(3,4) = 1+1+1+1+2+1+2+1+1+2+5+2+2+5+2+1+2+2+2+5 = 41.

MAPLE

Row := proc(n, len) local C, ogf, ser; C := (1-sqrt(1-4*x))/(2*x);

ogf := C^n*x/(1-x); ser := series(ogf, x, (n+1)*len+1);

seq(coeff(ser, x, j), j=0..len) end:

for n from 0 to 9 do Row(n, 9) od;

# Alternatively by recurrence:

B := proc(n, k) option remember; if n <= 0 or k < 0 then 0

elif n = k then 1 else B(n-1, k) + B(n, k-1) fi end:

A := (n, k) -> B(n + k, k): seq(lprint(seq(A(n, k), k=0..9)), n=0..9);

MATHEMATICA

(* Illustrating the sum formula, not efficient. *) T[0, K_] := Boole[K != 0];

T[N_, K_] := Module[{}, r[n_, k_] := FrobeniusSolve[ConstantArray[1, n], k];

X[n_] := Flatten[Table[r[N, j], {j, 0, n - 1}], 1];

Sum[Product[CatalanNumber[m[[i]]], {i, 1, N}], {m , X[K]}]];

Trow[n_] := Table[T[n, k], {k, 0, 9}]; Table[Trow[n], {n, 0, 9}]

CROSSREFS

The coefficients of the polynomials generating the columns are in A323233.

Sums of antidiagonals and row 1 are A014137. Main diagonal is A242798.

Rows: A057427 (n=0), A014137 (n=1), A014138 (n=2), A001453 (n=3), A114277 (n=4), A143955 (n=5).

Columns: A000027 (k=2), A034856 (k=3), A323221 (k=4), A323220 (k=5).

Similar array based on central binomials is A323222.

Sequence in context: A261835 A286932 A259475 * A118340 A213276 A210391

Adjacent sequences:  A323221 A323222 A323223 * A323225 A323226 A323227

KEYWORD

nonn,tabl

AUTHOR

Peter Luschny, Jan 24 2019

STATUS

approved

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Last modified September 21 19:59 EDT 2019. Contains 327282 sequences. (Running on oeis4.)