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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A306210 T(n,k) = binomial(n + k, n) - binomial(n + floor(k/2), n) + 1, square array read by descending antidiagonals (n >= 0, k >= 0).

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 2, 3, 1, 1, 3, 4, 4, 1, 1, 3, 8, 7, 5, 1, 1, 4, 10, 17, 11, 6, 1, 1, 4, 16, 26, 31, 16, 7, 1, 1, 5, 19, 47, 56, 51, 22, 8, 1, 1, 5, 27, 65, 112, 106, 78, 29, 9, 1, 1, 6, 31, 101, 176, 232, 183, 113, 37, 10, 1, 1, 6, 41, 131, 296, 407, 435, 295, 157, 46, 11, 1
Offset: 0

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Comments

There are at most T(n,k) possible values for the number of knots in an interpolatory cubature formula of degree k for an integral over an n-dimensional region.

Examples

			Square array begins:
  1, 1,  1,   1,   1,    1,    1,    1,     1,  ...
  1, 2,  2,   3,   3,    4,    4,    5,     5,  ...
  1, 3,  4,   8,  10,   16,   19,   27,    31,  ...
  1, 4,  7,  17,  26,   47,   65,  101,   131,  ...
  1, 5, 11,  31,  56,  112,  176,  296,   426,  ...
  1, 6, 16,  51, 106,  232,  407,  737,  1162,  ...
  1, 7, 22,  78, 183,  435,  841, 1633,  2794,  ...
  1, 8, 29, 113, 295,  757, 1597, 3313,  6106,  ...
  1, 9, 37, 157, 451, 1243, 2839, 6271, 12376,  ...
  ...
As triangular array, this begins:
  1;
  1, 1;
  1, 2,  1;
  1, 2,  3,  1;
  1, 3,  4,  4,  1;
  1, 3,  8,  7,  5,  1;
  1, 4, 10, 17, 11,  6,  1;
  1, 4, 16, 26, 31, 16,  7, 1;
  1, 5, 19, 47, 56, 51, 22, 8, 1;
  ...
		

Crossrefs

Programs

  • Mathematica
    T[n_, k_] = Binomial[n + k, n] - Binomial[n + Floor[k/2], n] + 1;
    Table[T[k, n - k], {k, 0, n}, {n, 0, 20}] // Flatten
  • Maxima
    T(n, k) := binomial(n + k, n) - binomial(n + floor(k/2), n) + 1$
    create_list(T(k, n - k), n, 0, 20, k, 0, n);

Formula

T(n,k) = A007318(n+k,n) - A046854(n+k,n) + 1.
G.f.: (1 - x - x^2 + x^3 - 2*y + 2*x*y + y^2 - x*y^2 + x^2*y^2)/((1 - x)*(1 - y)*(1 - x - y)*(1 - x^2 - y)).
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