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.

A366141 Triangular array read by rows: T(n,k) is the number of Boolean relation matrices such that all of the blocks of its Frobenius normal form are 0-blocks or 1-blocks and that have exactly k 1-blocks on the diagonal, n>=0, 0<=k<=n.

Original entry on oeis.org

1, 1, 1, 3, 7, 3, 25, 85, 84, 25, 543, 2335, 3579, 2322, 543, 29281, 152101, 310020, 309725, 151835, 29281, 3781503, 23139487, 58538763, 78349050, 58514700, 23128233, 3781503, 1138779265, 8051910805, 24318772884, 40667112045, 40664902810, 24315521720, 8050866418, 1138779265
Offset: 0

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Author

Geoffrey Critzer, Sep 30 2023

Keywords

Comments

A 1(0) block is such that every entry in the block is 1(0).
Conjecture: lim_{n -> oo} T(n,k)/T(n,n-k) = 1.

Examples

			Triangle begins ...
        1;
        1,        1;
        3,        7,        3;
       25,       85,       84,       25;
      543,     2335,     3579,     2322,      543;
    29281,   152101,   310020,   309725,   151835,    29281;
  3781503, 23139487, 58538763, 78349050, 58514700, 23128233, 3781503;
  ...
		

Crossrefs

Cf. A365593 (row sums), A003024.

Programs

  • Mathematica
    nn = 6; B[n_] := 2^Binomial[n, 2] n!; dags=Select[Import["https://oeis.org/A003024/b003024.txt", "Table"],
       Length@# == 2 &][[All, 2]]; d[x_] := Total[dags Table[x^i/i!, {i, 0, 40}]];
    Map[Select[#, # > 0 &] &,Table[n!, {n, 0, nn}] CoefficientList[
        Series[d[y (Exp[x] - 1) + x], {x, 0, nn}], {x, y}]] // Grid

Formula

T(n,0) = T(n,n) = A003024(n).
E.g.f.: D(y(exp(x)-1)+x) where D(x) is the e.g.f. for A003024.