cp's OEIS Frontend

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.

A026148 Irregular triangular array T read by rows: T(n,0) = 1 for i >= 0, T(1,1) = 1,T(2,1) = 1, T(2,2) = 2, T(2,3) = 1, T(2,4) = 1 and for n >= 3, T(n,1) = n-1, T(n,k) = T(n-1,k-2) + T(n-1,k-1) + T(n-1,k) for k=2,...,n+1, and T(n, k+2) = T(n-1, k) + T(n-1, k+1).

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 4, 4, 4, 2, 1, 3, 7, 10, 12, 10, 6, 1, 4, 11, 20, 29, 32, 28, 16, 1, 5, 16, 35, 60, 81, 89, 76, 44, 1, 6, 22, 56, 111, 176, 230, 246, 209, 120, 1, 7, 29, 84, 189, 343, 517, 652, 685, 575, 329, 1, 8, 37, 120, 302, 616, 1049, 1512, 1854, 1912, 1589, 904, 1, 9, 46, 165
Offset: 1

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Examples

			First 7 rows:
  1
  1  1
  1  1  2  1  1
  1  2  4  4  4  2
  1  3  7 10 12 10  6
  1  4 11 20 29 32 28 16
  1  5 16 35 60 81 89 76 44
		

Programs

  • Mathematica
    z = 12; t[n_, 0] = 1; t[1, 1] = 1; t[2, 2] = 2; t[2, 3] = 1; t[2, 4] = 1; t[n_, 1] := t[n, 1] = n - 1; t[n_, k_] := t[n, k] = Which[2 <= k <= n + 1, t[n - 1, k - 2] + t[n - 1, k - 1] + t[n - 1, k], k == n + 2, t[n - 1, k - 2] + t[n - 1, k - 1]]; u = Join[{{1}}, {{1, 1}}, Table[t[n, k], {n, 2, z}, {k, 0, n + 2}]]; TableForm[u] (* A026148 array *)
    Flatten[u] (* A026148 sequence *) (*  Clark Kimberling, Aug 28 2014 *)

Extensions

Definition clarified and Example by Clark Kimberling, Aug 28 2014