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 1-8 of 8 results.

A089934 Table T(n,k) of the number of n X k matrices on {0,1} without adjacent 0's in any row or column.

Original entry on oeis.org

2, 3, 3, 5, 7, 5, 8, 17, 17, 8, 13, 41, 63, 41, 13, 21, 99, 227, 227, 99, 21, 34, 239, 827, 1234, 827, 239, 34, 55, 577, 2999, 6743, 6743, 2999, 577, 55, 89, 1393, 10897, 36787, 55447, 36787, 10897, 1393, 89, 144, 3363, 39561, 200798, 454385, 454385, 200798
Offset: 1

Views

Author

Marc LeBrun, Nov 15 2003

Keywords

Comments

Recurrence orders are A089935. n X 1/1 X n patterns interpreted as binary values is A003714.
Number of independent vertex sets in the P_n X P_k grid graph. - Andrew Howroyd, Jun 06 2017
All columns (or rows) are linear recurrences with constant coefficients and order of the recurrence <= A001224(k+1). - Andrew Howroyd, Dec 24 2019
The enumeration of tiling "W-shaped" polyominoes in a (n+1) X (k+1) rectangle, whose shapes are (no flipping or rotating allowed):
.. .._. ... ...
|| ||_| .||_| .||_|
|| ||_| .||_|
|| ||_|
|| ... - _Liang Kai, Apr 19 2025

Examples

			Table starts:
  ========================================================
  n\k|  1   2     3      4       5        6          7
  ---|----------------------------------------------------
  1  |  2   3     5      8      13       21         34 ...
  2  |  3   7    17     41      99      239        577 ...
  3  |  5  17    63    227     827     2999      10897 ...
  4  |  8  41   227   1234    6743    36787     200798 ...
  5  | 13  99   827   6743   55447   454385    3729091 ...
  6  | 21 239  2999  36787  454385  5598861   69050253 ...
  7  | 34 577 10897 200798 3729091 69050253 1280128950 ...
  ... - _Andrew Howroyd_, Jun 06 2017
a(2,2)=7:
  11 11 11 10 10 01 01
  11 10 01 11 01 11 10
		

Crossrefs

T(n, 0) = T(0, m) = 1. Zero based table is A089980.
Main diagonal is A006506.
Cf. A089935, A001224, A197054 (maximal independent sets), A218354, A003714.

Programs

  • PARI
    step(v, S)={vector(#v, i, sum(j=1, #v, v[j]*!bitand(S[i], S[j])))}
    mkS(k)={select(b->!bitand(b,b>>1), [0..2^k-1])}
    T(n,k)={my(S=mkS(k), v=vector(#S, i, i==1)); for(n=1, n, v=step(v,S)); vecsum(v)} \\ Andrew Howroyd, Dec 24 2019

A051737 Number of 4 X n (0,1)-matrices with no consecutive 1's in any row or column.

Original entry on oeis.org

1, 8, 41, 227, 1234, 6743, 36787, 200798, 1095851, 5980913, 32641916, 178150221, 972290957, 5306478436, 28961194501, 158061670175, 862654025422, 4708111537971, 25695485730239, 140238391149386, 765379824048327, 4177217595760125, 22798023012345528, 124424893212114297
Offset: 0

Views

Author

Stephen G Penrice, Dec 06 1999

Keywords

Crossrefs

Row 4 of A089934.
Cf. A051736.

Programs

  • Mathematica
    LinearRecurrence[{4, 9, -5, -4, 1}, {1, 8, 41, 227, 1234}, 24] (* Jean-François Alcover, Nov 05 2017 *)
  • PARI
    Vec((1+4*x-4*x^3+x^4)/(1-4*x-9*x^2+5*x^3+4*x^4-x^5) + O(x^50)) \\ Michel Marcus, Sep 17 2014

Formula

From Yong Kong (ykong(AT)curagen.com), Dec 24 2000: (Start)
a(n) = 4*a(n - 1) + 9*a(n - 2) - 5*a(n - 3) - 4*a(n - 4) + a(n - 5);
G.f.: (1 + 4*x - 4*x^3 + x^4)/(1 - 4*x - 9*x^2 + 5*x^3 + 4*x^4 - x^5). (End)
a(n) = 2*a(n - 1) + 18*a(n - 2) + 9*a(n - 3) - 23*a(n - 4) - 2*a(n - 5) + 6*a(n - 6) - a(n - 7).

Extensions

More terms from James Sellers, Dec 08 1999
More terms from Michel Marcus, Sep 17 2014

A089936 Number of 5 X n matrices with entries {0,1} without adjacent 0's in any row or column. 5th row of A089934.

Original entry on oeis.org

13, 99, 827, 6743, 55447, 454385, 3729091, 30584687, 250916131, 2058249165, 16884649135, 138508056265, 1136221529549, 9320704799431, 76460212316453, 627222736888811, 5145271430670385, 42207992410219447, 346243111960194009
Offset: 1

Views

Author

Marc LeBrun, Nov 15 2003

Keywords

Comments

Row/columns 1 through 7 are A000045, A001333, A051736, A051737, A089936, A089937, A089938.
Number of independent vertex sets in the grid graph P_5 X P_n. - Andrew Howroyd, Jun 06 2017

Crossrefs

Formula

G.f.: x*(13 + 47*x - 37*x^2 - 129*x^3 + 68*x^4 + 49*x^5 - 23*x^6 - 3*x^7 + x^8) / (1 - 4*x - 36*x^2 + 105*x^4 - 15*x^5 - 64*x^6 + 20*x^7 + 4*x^8 - x^9) (conjectured). - Colin Barker, Jun 06 2017
The above conjecture is correct since the order of the recurrence is A089935(5) = 9. - Andrew Howroyd, Dec 24 2019

A089937 Number of 6 X n matrices with entries {0,1} without adjacent 0's in any row or column. 6th row of A089934.

Original entry on oeis.org

21, 239, 2999, 36787, 454385, 5598861, 69050253, 851302029, 10496827403, 129422885699, 1595777230271, 19675706193157, 242599324206721, 2991220223776445, 36881397137844409, 454743263319217787, 5606930966068061311, 69132797971282998447
Offset: 1

Views

Author

Marc LeBrun, Nov 15 2003

Keywords

Comments

Row/columns 1 through 7 are A000045, A001333, A051736, A051737, A089936, A089937, A089938.
Number of independent vertex sets in the grid graph P_6 X P_n. - Andrew Howroyd, Jun 06 2017

Crossrefs

Formula

G.f.: x*(21 + 71*x - 215*x^2 - 385*x^3 + 668*x^4 + 234*x^5 - 400*x^6 + 9*x^7 + 49*x^8 - 3*x^9 - x^10) / (1 - 8*x - 62*x^2 + 78*x^3 + 375*x^4 - 300*x^5 - 486*x^6 + 385*x^7 + 30*x^8 - 52*x^9 + 2*x^10 + x^11) (conjectured). - Colin Barker, Jun 06 2017
The above conjecture is correct because the order of the recurrence is A089935(6) = 11. - Andrew Howroyd, Dec 24 2019

Extensions

Terms a(17) and beyond from Andrew Howroyd, Jun 06 2017

A089938 Number of 7 X n matrices with entries {0,1} without adjacent 0's in any row or column. 7th row of A089934.

Original entry on oeis.org

34, 577, 10897, 200798, 3729091, 69050253, 1280128950, 23720149995, 439621976195, 8147000813446, 150985649174085, 2798109826697003, 51855860689753372, 961012671564107667, 17809889025037476097, 330060028036299469334, 6116807668464485142495
Offset: 1

Views

Author

Marc LeBrun, Nov 15 2003

Keywords

Comments

Row/columns 1 through 7 are A000045, A001333, A051736, A051737, A089936, A089937, A089938.
Number of independent vertex sets in the grid graph P_7 X P_n. - Andrew Howroyd, Jun 06 2017

Crossrefs

Formula

O.g.f.: - (X - 1)*(X^19 + 10*X^18 - 58*X^17 - 576*X^16 + 651*X^15 + 8054*X^14 - 5381*X^13 - 42910*X^12 + 32530*X^11 + 90357*X^10 - 90813*X^9 - 52366*X^8 + 79558*X^7 - 8263*X^6 - 13918*X^5 + 2501*X^4 + 894*X^3 - 94*X^2 - 26*X - 1)/(X^21 + 9*X^20 - 87*X^19 - 546*X^18 + 2227*X^17 + 9369*X^16 - 25564*X^15 - 54187*X^14 + 139011*X^13 + 100779*X^12 - 340142*X^11 + 21372*X^10 + 308107*X^9 - 127405*X^8 - 82823*X^7 + 48558*X^6 + 6975*X^5 - 5659*X^4 - 210*X^3 + 203*X^2 + 9*X - 1)

Extensions

Terms a(16) and beyond from Andrew Howroyd, Jun 06 2017

A371967 Irregular triangle T(r,w) read by rows: number of ways of placing w non-attacking wazirs on a 3 X r board.

Original entry on oeis.org

1, 1, 3, 1, 1, 6, 8, 2, 1, 9, 24, 22, 6, 1, 1, 12, 49, 84, 61, 18, 2, 1, 15, 83, 215, 276, 174, 53, 9, 1, 1, 18, 126, 442, 840, 880, 504, 158, 28, 2, 1, 21, 178, 792, 2023, 3063, 2763, 1478, 472, 93, 12, 1, 1, 24, 239, 1292, 4176, 8406, 10692, 8604, 4374, 1416, 297, 38, 2, 1, 27, 309
Offset: 0

Views

Author

R. J. Mathar, Apr 14 2024

Keywords

Examples

			The triangle starts with r>=0 rows and w>=0 wazirs as
  1 ;
  1 3 1 ;
  1 6 8 2  ;
  1 9 24 22 6 1 ;
  1 12 49 84 61 18 2  ;
  1 15 83 215 276 174 53 9 1 ;
  1 18 126 442 840 880 504 158 28 2  ;
  1 21 178 792 2023 3063 2763 1478 472 93 12 1 ;
  1 24 239 1292 4176 8406 10692 8604 4374 1416 297 38 2  ;
  1 27 309 1969 7731 19591 32716 36257 26674 13035 4264 945 142 15 1 ;
  ...
		

Crossrefs

Cf. A051736 (row sums), A035607 (on 2Xr board), A011973 (on 1Xr board), A232833 (on rXr board).
T(n,n) gives A371978.
Row maxima give A371979.
Cf. A007494.

Programs

  • Maple
    b:= proc(n, l) option remember; `if`(n=0, 1,
          add(`if`(Bits[And](j, l)>0, 0, expand(b(n-1, j)*
          x^add(i, i=Bits[Split](j)))), j=[0, 1, 2, 4, 5]))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=0..degree(p)))(b(n, 0)):
    seq(T(n), n=0..10);  # Alois P. Heinz, Apr 14 2024
  • Mathematica
    b[n_, l_] := b[n, l] = If[n == 0, 1, Sum[If[BitAnd[j, l] > 0, 0, Expand[b[n - 1, j]*x^DigitCount[j, 2, 1]]], {j, {0, 1, 2, 4, 5}}]];
    T[n_] := CoefficientList[b[n, 0], x];
    Table[T[n], {n, 0, 10}] // Flatten (* Jean-François Alcover, Jun 05 2024, after Alois P. Heinz *)

Formula

T(r,0) = 1.
T(r,1) = 3*r.
T(r,2) = A064225(r-1).
T(r,3) = A172229(r).
T(r,4) = 27*r^4/8 -117*r^3/4 +829*r^2/8 -715*r/4 +126. [Siehler Table 3]
T(3,w) = A232833(3,w).
G.f.: (1+x*y) *(1 +x*y +x*y^2 -x^2*y^3)/(1 -x -x*y -x^2*y^3 -2*x^2*y -3*x^2*y^2 -x^3*y^2 +x^3*y^4 +x^4*y^4). - R. J. Mathar, Apr 21 2024

A089935 a(n) = order of recurrence generating row (or column) n of A089934.

Original entry on oeis.org

2, 2, 4, 5, 9, 11, 21, 30, 51, 76, 127, 195, 322, 504, 826
Offset: 1

Views

Author

Marc LeBrun, Nov 15 2003

Keywords

Comments

The only known value where a(n) is strictly less than the theoretical upper bound A001224(n+1) is a(6) = 11. - Andrew Howroyd, Dec 24 2019

Examples

			a(2)=2 because the recurrence relation for the second row/column is a(n) = 2 a(n-1) + a(n-2).
		

Crossrefs

Row/columns 1 through 7 of A089934 are A000045, A001333, A051736, A051737, A089936, A089937, A089938.
Cf. A001224.

Formula

a(n) <= A001224(n+1). - Andrew Howroyd, Dec 24 2019

Extensions

a(8)-a(10) from Andrew Howroyd, Dec 24 2019
a(11)-a(15) from Max Alekseyev, Dec 12 2024

A089939 T(i,j) = 1 if F(i) AND F(j) = 0, otherwise 0, where F is A003714 and AND is the bitwise logical-and operation. Table read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1
Offset: 0

Views

Author

Marc LeBrun, Nov 15 2003

Keywords

Comments

Encodes which row/column patterns may be adjacent in 01-matrices where no two 0 elements may be adjacent. Contains many interesting recursive patterns such as Fibonacci-sized blocks of 0's along main diagonal.

Examples

			T(3,4) = 0 because F(3) AND F(4) = 4 AND 5 = 1, which is nonzero.
		

Crossrefs

Cf. A003714 (Fibbinary), A005614 (row or column 1).

Extensions

Name clarified by Jon E. Schoenfield, Aug 19 2022
Showing 1-8 of 8 results.