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.

Showing 1-6 of 6 results.

A348815 a(n) = number of chord labeled loopless diagrams by number of K_4.

Original entry on oeis.org

0, 1, 134, 75843, 83002866, 158861646466, 490294453324924, 2292204611710892971, 15459367618357013402267, 144663877588996810362218074, 1819753109993633276315632934129, 29976383544377113242613349012354566, 632574848906117234957565158900144038734
Offset: 1

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Author

Michael De Vlieger, Nov 01 2021

Keywords

Crossrefs

Extensions

a(11) onwards from Andrew Howroyd, Feb 05 2024

A369923 Array read by antidiagonals: A(n,k) is the number of permutations of n copies of 1..k with values introduced in order and without cyclically adjacent elements equal.

Original entry on oeis.org

0, 1, 0, 1, 1, 0, 1, 4, 1, 0, 1, 31, 22, 1, 0, 1, 293, 1415, 134, 1, 0, 1, 3326, 140343, 75843, 866, 1, 0, 1, 44189, 20167651, 83002866, 4446741, 5812, 1, 0, 1, 673471, 3980871156, 158861646466, 55279816356, 276154969, 40048, 1, 0
Offset: 1

Views

Author

Andrew Howroyd, Feb 05 2024

Keywords

Comments

Also, T(n,k) is the number of generalized chord labeled loopless diagrams with k parts of K_n. See the Krasko reference for a full definition.

Examples

			Array begins:
n\k| 1 2    3         4              5                    6 ...
---+-----------------------------------------------------------
 1 | 0 1    1         1              1                    1 ...
 2 | 0 1    4        31            293                 3326 ...
 3 | 0 1   22      1415         140343             20167651 ...
 4 | 0 1  134     75843       83002866         158861646466 ...
 5 | 0 1  866   4446741    55279816356     1450728060971387 ...
 6 | 0 1 5812 276154969 39738077935264 14571371516350429940 ...
 ...
		

Crossrefs

Column 3 is A197657, column 4 appears to be A209183(n)/2.
Cf. A322013 (without linearly adjacent elements equal), A322093.

Programs

  • Mathematica
    T[n_, k_] := If[k == 1, 0, Expand[(-1)^(k (n + 1))/(k - 1)! n Hypergeometric1F1[1 - n, 2, x]^k x^(k - 1)] /. x^p_ :> p!] (* Eric W. Weisstein, Feb 20 2025 *)
  • PARI
    \\ compare with A322013.
    q(n, x) = sum(i=1, n, (-1)^(n-i) * binomial(n-1, n-i) * x^i/i!)
    T(n, k) = if(k > 1, subst(serlaplace(n*q(n, x)^k/x), x, 1)/(k-1)!, 0)

A348813 a(n) = number of chord labeled loopless diagrams by number of K_3.

Original entry on oeis.org

0, 1, 22, 1415, 140343, 20167651, 3980871156, 1035707510307, 343866839138005, 141979144588872613, 71386289535825383386, 42954342000612934599071, 30482693813120122213093587, 25196997894058490607106028095, 24001522306527907199721466108488, 26102037346800387738363882455862531
Offset: 1

Views

Author

Michael De Vlieger, Nov 01 2021

Keywords

Crossrefs

Extensions

a(14) onwards from Andrew Howroyd, Feb 05 2024

A348818 a(n) = number of chord labeled loopless diagrams by number of K_5.

Original entry on oeis.org

0, 1, 866, 4446741, 55279816356, 1450728060971387, 72078730629785795963, 6235048155225093080061949, 879601407931825739964190440635, 192100729970218737700046212217095291, 62258393664270652226502315136978421947948, 28913744296806659870889046765907226809528931041
Offset: 1

Views

Author

Michael De Vlieger, Nov 01 2021

Keywords

Crossrefs

Extensions

a(9) onwards from Andrew Howroyd, Feb 05 2024

A348822 a(n) = number of loopless diagrams by number of K_6 up to rotational symmetry.

Original entry on oeis.org

0, 1, 335, 11508322, 1324603148183, 404760320241653655, 282780723811372935744420
Offset: 1

Views

Author

Michael De Vlieger, Nov 01 2021

Keywords

Crossrefs

A348823 a(n) = number of loopless diagrams by number of K_6 up to all symmetries.

Original entry on oeis.org

0, 1, 203, 5765385, 662305416760, 202380163158922023, 141390361908351519807928
Offset: 1

Views

Author

Michael De Vlieger, Nov 01 2021

Keywords

Crossrefs

Showing 1-6 of 6 results.