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 1-7 of 7 results.

A189508 Column 2 of triangle in A189507.

Original entry on oeis.org

1, 3, 21, 160, 1620, 19068, 264420, 4166880, 74011488, 1459381440, 31674232128
Offset: 1

Views

Author

N. J. A. Sloane, Apr 23 2011

Keywords

Crossrefs

Cf. A189507.

Extensions

Added missing term for n=9, Anthony Labarre, Feb 14 2013

A189509 Column 3 of triangle in A189507.

Original entry on oeis.org

1, 6, 65, 701, 9324, 138016, 2325740, 43448940, 897020784, 20241273264
Offset: 2

Views

Author

N. J. A. Sloane, Apr 23 2011

Keywords

Crossrefs

Cf. A189507.

Extensions

Added missing term for n=9, Anthony Labarre, Feb 14 2013

A164652 Triangle read by rows: Hultman numbers: a(n,k) is the number of permutations of n elements whose cycle graph (as defined by Bafna and Pevzner) contains k cycles for n >= 0 and 1 <= k <= n+1.

Original entry on oeis.org

1, 0, 1, 1, 0, 1, 0, 5, 0, 1, 8, 0, 15, 0, 1, 0, 84, 0, 35, 0, 1, 180, 0, 469, 0, 70, 0, 1, 0, 3044, 0, 1869, 0, 126, 0, 1, 8064, 0, 26060, 0, 5985, 0, 210, 0, 1, 0, 193248, 0, 152900, 0, 16401, 0, 330, 0, 1, 604800, 0, 2286636, 0, 696905, 0, 39963, 0, 495, 0, 1, 0, 19056960, 0, 18128396, 0, 2641925, 0, 88803, 0, 715, 0, 1
Offset: 0

Views

Author

Anthony Labarre, Aug 19 2009

Keywords

Comments

a(n,k) is also the number of ways to express a given (n+1)-cycle as the product of an (n+1)-cycle and a permutation with k cycles (see Doignon and Labarre). a(n,n+1-2k) is the number of permutations of n elements whose block-interchange distance is k (see Christie, Doignon and Labarre).
Named after the Swedish mathematician Axel Hultman. - Amiram Eldar, Jun 11 2021
a(2*n,1) is the number of spanning trees in certain graphs with 2*n+1 vertices and n*(n+1) edges (see Ishikawa, Miezaki, and Tanaka). - Tsuyoshi Miezaki, Feb 08 2023

Examples

			Triangle begins:
  n=0:  1;
  n=1:  0, 1;
  n=2:  1, 0, 1;
  n=3:  0, 5, 0, 1;
  n=4:  8, 0, 15, 0, 1;
  n=5:  0, 84, 0, 35, 0, 1;
  n=6:  180, 0, 469, 0, 70, 0, 1;
  n=7:  0, 3044, 0, 1869, 0, 126, 0, 1;
  n=8:  8064, 0, 26060, 0, 5985, 0, 210, 0, 1;
  n=9:  0, 193248, 0, 152900, 0, 16401, 0, 330, 0, 1;
  n=10: 604800, 0, 2286636, 0, 696905, 0, 39963, 0, 495, 0, 1;
  ...
From _Jon E. Schoenfield_, May 20 2023: (Start)
As a right-aligned triangle:
                                                      1; n=0
                                                   0, 1; n=1
                                                1, 0, 1; n=2
                                           0,   5, 0, 1; n=3
                                        8, 0,  15, 0, 1; n=4
                                 0,    84, 0,  35, 0, 1; n=5
                            180, 0,   469, 0,  70, 0, 1; n=6
                      0,   3044, 0,  1869, 0, 126, 0, 1; n=7
                8064, 0,  26060, 0,  5985, 0, 210, 0, 1; n=8
          0,  193248, 0, 152900, 0, 16401, 0, 330, 0, 1; n=9
  604800, 0, 2286636, 0, 696905, 0, 39963, 0, 495, 0, 1; n=10
  ...
(End)
		

References

  • Axel Hultman, Toric permutations, Master's thesis, Department of Mathematics, KTH, Stockholm, Sweden, 1999.

Crossrefs

Cf. A185263 (rows reversed without 0's).

Programs

  • Haskell
    a164652 n k = a164652_tabl !! n !! k
    a164652_row n = a164652_tabl !! n
    a164652_tabl = [0] : tail (zipWith (zipWith (*)) a128174_tabl $
       zipWith (map . flip div) (tail a000217_list) (map init $ tail a130534_tabl))
    -- Reinhard Zumkeller, Aug 01 2014
    
  • Maple
    A164652:= (n, k)-> `if`(n-k mod 2 = 1, -Stirling1(n+2, k)/binomial(n+2, 2), 0):
    for n from 0 to 7 do seq(A164652(n,k),k=1..n+1) od; # Peter Luschny, Mar 22 2015
  • Mathematica
    T[n_, k_] := If[OddQ[n-k], Abs[StirlingS1[n+2, k]]/Binomial[n+2, 2], 0];
    Table[T[n, k], {n, 0, 11}, {k, 1, n+1}] // Flatten (* Jean-François Alcover, Aug 10 2018 *)
  • PARI
    T(n,k)= my(s=(n-k)%2); (-1)^s*s*stirling(n+2,k,1)/binomial(n+2,2);
    concat(vector(12, n, vector(n, k, T(n-1,k)))) \\ Gheorghe Coserea, Jan 23 2018
  • Sage
    def A164652(n, k):
        return stirling_number1(n+2,k)/binomial(n+2,2) if is_odd(n-k) else 0
    for n in (0..7): print([A164652(n,k) for k in (1..n+1)]) # Peter Luschny, Mar 22 2015
    

Formula

T(n,k) = S1(n+2,k)/C(n+2,2) if n-k is odd, and 0 otherwise. Here S1(n,k) are the unsigned Stirling numbers of the first kind A132393 and C(n,k) is the binomial coefficient (see Bona and Flynn).
For n > 0: T(n,k) = A128174(n+1,k) * A130534(n+1,k-1) / A000217(n+1). - Reinhard Zumkeller, Aug 01 2014
n-th row polynomial R(n,x) = (x/2)*( P(n+1,x) + (-1)^n * P(n+1,-x) ) / binomial(n+2,2), where P(k,x) = (x + 1)*(x + 2)*...*(x + k). - Peter Bala, May 14 2023

Extensions

T(0,1) set to 1 by Peter Luschny, Mar 24 2015
Edited to match values of k to the range 1 to n+1. - Max Alekseyev, Nov 20 2020

A264614 Irregular triangle read by rows: T(n,k) = number of unsigned unichromosonal genomes with n genes at 3-break distance k from a fixed genome, 0 <= k <= floor(n/2).

Original entry on oeis.org

1, 1, 0, 1, 1, 1, 4, 1, 1, 10, 13, 1, 20, 75, 24, 1, 35, 287, 397, 1, 56, 854, 3112, 1017, 1, 84, 2142, 16196, 21897, 1, 120, 4746, 64520, 222573, 70920, 1, 165, 9570, 212498, 1486749, 1919817, 1, 220, 17919, 606584, 7503815, 24312636, 7475625, 1, 286, 31603, 1548404, 30891575, 200350670, 246179061
Offset: 1

Views

Author

N. J. A. Sloane, Nov 28 2015

Keywords

Examples

			Triangle begins:
1,
1,0,
1,1,
1,4,1,
1,10,13,
1,20,75,24,
1,35,287,397,
1,56,854,3112,1017,
1,84,2142,16196,21897,
...
		

Crossrefs

Extensions

Extended and offset corrected by Max Alekseyev, Feb 13 2018

A264615 Irregular triangle read by rows: T(n,k) = number of signed unichromosonal genomes with n genes at 3-break distance k from a fixed genome, 0 <= k <= floor(n/2).

Original entry on oeis.org

1, 1, 1, 1, 7, 1, 22, 25, 1, 50, 333, 1, 95, 1851, 1893, 1, 161, 6839, 39079, 1, 252, 19782, 323580, 301505, 1, 372, 48510, 1706180, 8566857, 1, 525, 105546, 6792650, 95942613, 82953225, 1, 715, 209682, 22248446, 668057885, 3025374471, 1, 946, 387783, 63055388, 3435912383, 43154349714, 35095900185
Offset: 1

Views

Author

N. J. A. Sloane, Nov 28 2015

Keywords

Examples

			Triangle begins:
1,
1,1,
1,7,
1,22,25,
1,50,333,
1,95,1851,1893,
1,161,6839,39079,
1,252,19782,323580,301505,
1,372,48510,1706180,8566857,
...
		

Crossrefs

Extensions

Extended and offset corrected by Max Alekseyev, Feb 13 2018

A264616 Irregular triangle read by rows: T(n,k) = number of unsigned unichromosonal genomes with n genes at 4-break distance k from a fixed genome, 0 <= k <= floor((n+1)/3).

Original entry on oeis.org

1, 1, 0, 1, 1, 1, 5, 1, 15, 8, 1, 35, 84, 1, 70, 649, 1, 126, 3585, 1328, 1, 210, 14949, 25160, 1, 330, 50421, 312128, 1, 495, 144903, 2621465, 861936, 1, 715, 367983, 16015637, 23532464, 1, 1001, 847275, 76717355, 401435968, 1, 1365, 1801943, 304775471, 4519766436, 1400675584
Offset: 1

Views

Author

N. J. A. Sloane, Nov 28 2015

Keywords

Examples

			Triangle begins:
1,
1,0,
1,1,
1,5,
1,15,8,
1,35,84,
1,70,649,
1,126,3585,1328,
1,210,14949,25160,
...
		

Crossrefs

Extensions

Extended and offset corrected by Max Alekseyev, Feb 13 2018

A264617 Irregular triangle read by rows: T(n,k) = number of signed unichromosonal genomes with n genes at 4-break distance k from a fixed genome, 0 <= k <= floor((n+1)/3).

Original entry on oeis.org

1, 1, 1, 1, 7, 1, 47, 1, 175, 208, 1, 470, 3369, 1, 1036, 45043, 1, 2002, 315213, 327904, 1, 3522, 1472157, 8846240, 1, 5775, 5287071, 180501713, 1, 8965, 15795483, 1908769247, 1791317504, 1, 13321, 41169051, 13068136571, 68640287456, 1, 19097, 96558891, 66722214923, 1895171760688
Offset: 1

Views

Author

N. J. A. Sloane, Nov 28 2015

Keywords

Examples

			Triangle begins:
1,
1,1,
1,7,
1,47,
1,175,208,
1,470,3369,
1,1036,45043,
1,2002,315213,327904,
1,3522,1472157,8846240,
...
		

Crossrefs

Extensions

Extended and offset corrected by Max Alekseyev, Feb 13 2018
Showing 1-7 of 7 results.