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.

A060438 Triangle T(n,k), 1 <= k <= n, giving maximal size of binary code of length n and covering radius k.

Original entry on oeis.org

1, 2, 1, 2, 2, 1, 4, 2, 2, 1, 7, 2, 2, 2, 1, 12, 4, 2, 2, 2, 1, 16, 7, 2, 2, 2, 2, 1, 32, 12, 4, 2, 2, 2, 2, 1, 62, 16, 7, 2, 2, 2, 2, 2, 1
Offset: 1

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Author

N. J. A. Sloane, Apr 07 2001

Keywords

Examples

			Triangle starts:
1;
2,1;
2,2,1;
4,2,2,1;
7,2,2,2,1;
...
		

References

  • G. D. Cohen et al., Covering Codes, North-Holland, 1997, p. 166.

Crossrefs

Columns give A000983, A029866. Cf. A060439, A060440.

Extensions

Row 9 from Andrey Zabolotskiy, Apr 11 2017 using Gerzson Kéri's tables.

A029866 Size of minimal binary covering code of length n and covering radius 2.

Original entry on oeis.org

1, 2, 2, 2, 4, 7, 12, 16
Offset: 2

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Author

Keywords

Comments

Also the domination number of the (n+1)-halved cube graph. - Eric W. Weisstein, Aug 31 2016 and Jul 17 2017 (after discussion with Stan Wagon)

References

  • G. D. Cohen et al., Covering Codes, North-Holland, 1997, p. 166.

Crossrefs

A column of A060438.
Cf. A000983 (domination number of the n-hypercube graph Q_n).

Extensions

a(9) from Andrey Zabolotskiy, Sep 01 2016

A238305 Triangle E(n,k), 1<=k<=n, giving the cardinality of optimal ternary covering codes of empty spheres of length n and radius k.

Original entry on oeis.org

2, 3, 3, 6, 4, 5, 14, 6, 5, 8, 27, 12, 6, 7, 12
Offset: 1

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Author

Kamiel P.F. Verstraten, Feb 24 2014

Keywords

Comments

The next term is in the range 71-81.
Right diagonal is equal to A086676.

Examples

			Triangle starts:
01: 2
02: 3 3
03: 6 4 5
04: 14 6 5 8
05: 27 12 6 7 12
...
		

Crossrefs

Related to A060439, which has a code consisting of filled spheres instead of empty spheres.
Related to A230014, the triangle giving the cardinality of optimal binary covering codes of empty spheres.
See also A000983.

A230014 Triangle E(n,k), 1<=k<=n, giving the cardinality of optimal binary covering codes of empty spheres of length n and radius k.

Original entry on oeis.org

2, 2, 4, 4, 4, 8, 4, 4, 4, 16, 8, 6, 6, 8, 32, 14, 8, 6, 8, 14, 64, 24, 8, 8, 8, 8, 24, 128, 32, 16, 8, 8, 8, 16, 32, 256, 64, 24, 12, 10, 10, 12, 24, 64, 512, 124
Offset: 1

Views

Author

Kamiel P.F. Verstraten, Feb 22 2014

Keywords

Comments

The next term is in the range 34-40.
Note that E(n,k) = E(n,n-k).

Examples

			Triangle starts:
01: 2,
02: 2, 4,
03: 4, 4, 8,
04: 4, 4, 4, 16,
05: 8, 6, 6, 8, 32,
06: 14, 8, 6, 8, 14, 64,
07: 24, 8, 8, 8, 8, 24, 128,
08: 32, 16, 8, 8, 8, 16, 32, 256,
09: 64, 24, 12, 10, 10, 12, 24, 64, 512,
10: 124, ...
		

Crossrefs

Related to A060438, which has a code consisting of filled spheres instead of empty spheres.
Related to A238305, the triangle giving the cardinality of optimal ternary covering codes of empty spheres.
The first column is equal to 2*A000983.

Extensions

a(43) corrected by Omar E. Pol, Nov 23 2014

A157887 The domatic number of the n-cube.

Original entry on oeis.org

1, 2, 2, 4, 4, 4, 5, 8, 8, 8
Offset: 0

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Author

Sune Kristian Jakobsen (sunejakobsen(AT)hotmail.com), Mar 08 2009

Keywords

Comments

It is known that a(n)=n+1 when n is of the form 2^k-1, and a(n)=a(n-1)a(m-1).
Patric R. J. Östergård proved that a_n/n->1 as n-> infinity. [From Sune Kristian Jakobsen (sunejakobsen(AT)hotmail.com), Mar 16 2009]
The value of A000983(9) = 62 means that any dominating set in G=HypercubeGraph[9] has size 62 or more. 9*62 > 512 so there cannot be 9 disjoint dominating sets in G. That there exist 8 disjoint dominating sets for G follows from the existence of 8 such sets for HypercubeGraph[8]: simply take any element in such a set and append both a 0 and 1 to it to turn it into a dominating set in dimension 9. The comment at A000983 about the dominating number for 10 being between 107 and 120 means that the domatic number here for n = 10 is either 8 or 9. - Stan Wagon, Jul 15 2017

Examples

			a(3)=4: The vertices of the 3-dimensional cube can be partitioned into 4 dominating sets, {000,111}, {001,110}, {010,101}, {011,100}, but not into 5. A subset of a graph is called dominating if every vertex in the graph is in the set or is a neighbor of a vertex in the set.
		

Extensions

a(9) from Stan Wagon, Jul 15 2017

A247181 Total domination number of the n-hypercube graph.

Original entry on oeis.org

2, 2, 4, 4, 8, 14, 24, 32, 64, 124
Offset: 1

Views

Author

Jernej Azarija, Nov 22 2014

Keywords

Comments

a(n) = size of smallest subset S of vertices of the n-cube Q_n such that every vertex of Q_n has a neighbor in S.
Proof for first formula can be found in the Verstraten link. - Kamiel P.F. Verstraten, Jun 10 2015

Examples

			a(1) = 2 since the complete graph on two vertices can only be totally dominated by taking both vertices.
		

Crossrefs

Cf. A000983 (half), A323515 (number of sets).

Formula

a(n) = 2*A000983(n-1), at least if 2<=n<=9. - Omar E. Pol, Nov 22 2014. This formula is true for all n>=2 (see Azarija-Henning-Klavžar paper). - Omar E. Pol, Jul 01 2016
a(n) = A230014(n,1), at least if 1<=n<=9. - Omar E. Pol, Nov 23 2014. This formula is true for all n>=1 (in accordance with the above comment). - Omar E. Pol, Jul 01 2016

Extensions

a(10) from Jernej Azarija, Jun 30 2016

A347555 Number of minimum dominating sets in the hypercube graph Q_n.

Original entry on oeis.org

1, 2, 6, 4, 40, 320, 2240, 240
Offset: 0

Views

Author

Eric W. Weisstein, Sep 06 2021

Keywords

Crossrefs

Cf. A000983 (minimum set size), A323515.

Extensions

a(6) from Christian Sievers, Nov 28 2023
a(7) from Christian Sievers, May 26 2024
Showing 1-7 of 7 results.