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.

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A059584 Triangle T(n,m) of number of labeled m-node T_0-hypergraphs with n hyperedges (empty hyperedges and multiple hyperedges included), m=0,1,...,2^n.

Original entry on oeis.org

1, 1, 1, 2, 2, 1, 3, 7, 12, 12, 1, 4, 16, 68, 292, 1120, 3360, 6720, 6720, 1, 5, 30, 235, 2251, 23520, 245280, 2412480, 21631680, 172972800, 1210809600, 7264857600, 36324288000, 145297152000, 435891456000, 871782912000, 871782912000
Offset: 0

Views

Author

Vladeta Jovovic, Goran Kilibarda, Jan 23 2001

Keywords

Comments

A hypergraph is a T_0 hypergraph if for every two distinct nodes there exists a hyperedge containing one but not the other node.

Examples

			Triangle starts:
1, 1;
1, 2, 2;
1, 3, 7, 12, 12;
1, 4, 16, 68, 292, 1120, 3360, 6720, 6720;
...
There are 7 2-node T_0-hypergraphs with 2 hyperedges: {{}, {1}}, {{}, {2}}, {{1}, {1}}, {{1}, {2}}, {{1}, {1, 2}}, {{2}, {2}} and {{2}, {1, 2}}.
		

Crossrefs

Cf. A059084, A051362 (=T(n,2)), A059585 (=T(n,3)), A059586 (row sums).

Formula

T(n,m) = Sum_{i=0..m} stirling1(m, i)*binomial(2^i+n-1, n).

A059585 Number of labeled 3-node T_0-hypergraphs with n hyperedges (empty hyperedges and multiple hyperedges included).

Original entry on oeis.org

0, 0, 12, 68, 235, 636, 1478, 3088, 5958, 10800, 18612, 30756, 49049, 75868, 114270, 168128, 242284, 342720, 476748, 653220, 882759, 1178012, 1553926, 2028048, 2620850, 3356080, 4261140, 5367492, 6711093, 8332860, 10279166, 12602368
Offset: 0

Views

Author

Vladeta Jovovic, Goran Kilibarda, Jan 23 2001

Keywords

Comments

A hypergraph is a T_0 hypergraph if for every two distinct nodes there exists a hyperedge containing one but not the other node.

Crossrefs

Cf. A059084, a(n)=A059584(n, 3), A059586.

Programs

  • Magma
    [n*(n-1)*(n+1)*(n^4+28*n^3+323*n^2+1988*n+ 4572)/5040: n in [0..35]]; // Vincenzo Librandi, Oct 07 2017
  • Maple
    for n from 0 to 100 do printf(`%d,`,n*(n - 1)*(n + 1)*(n^4 + 28*n^3 + 323*n^2 + 1988*n + 4572)/5040) od:
  • Mathematica
    CoefficientList[Series[x^2*(2 - x)^2*(3 - 4*x + 2*x^2)/(1 - x)^8, {x, 0, 50}], x] (* G. C. Greubel, Oct 06 2017 *)
    LinearRecurrence[{8, -28, 56, -70, 56, -28, 8, -1}, {0, 0, 12, 68, 235, 636, 1478, 3088}, 33] (* Vincenzo Librandi, Oct 07 2017 *)
  • PARI
    x='x+O('x^50); concat([0,0],Vec(x^2*(2-x)^2*(3-4*x+2*x^2)/(1-x)^8)) \\ G. C. Greubel, Oct 06 2017
    

Formula

a(n) = binomial(n + 7, n) - 3*binomial(n + 3, n) + 2*binomial(n + 1, n) = n*(n - 1)*(n + 1)*(n^4 + 28*n^3 + 323*n^2 + 1988*n + 4572)/5040.
G.f.: x^2*(2-x)^2*(3-4*x+2*x^2)/(1-x)^8. - Colin Barker, Jun 25 2012

Extensions

More terms from James Sellers, Jan 24 2001

A059587 T(n,m) = (1/m!)*Sum_{i=0..m} stirling1(m,i)*(2^i)*(2^i+1)*...*(2^i+n-1).

Original entry on oeis.org

1, 1, 1, 2, 1, 2, 6, 7, 4, 1, 6, 24, 48, 68, 73, 56, 28, 8, 1, 24, 120, 360, 940, 2251, 4704, 8176, 11488, 12876, 11440, 8008, 4368, 1820, 560, 120, 16, 1, 120, 720, 3000, 12720, 56660, 247016, 987252, 3480536, 10647035, 28163200, 64592320, 129068160
Offset: 0

Views

Author

Vladeta Jovovic, Jan 23 2001

Keywords

Examples

			Triangle starts:
1, 1;
1, 2, 1;
2, 6, 7, 4, 1;
6, 24, 48, 68, 73, 56, 28, 8, 1;
...
		

Crossrefs

Cf. A059084, (row sums) A059588.

Programs

  • Maple
    with(combinat): for n from 0 to 10 do for m from 0 to 2^n do printf(`%d,`,sum(abs(stirling1(n,i))*binomial(2^i, m), i=0..n)) od: od:

Formula

T(n, m) = Sum_{i=0..n} |stirling1(n, i)|*binomial(2^i, m).

Extensions

More terms from James Sellers, Jan 24 2001
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