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 1-5 of 5 results.

A286849 Array read by antidiagonals: T(m,n) = number of minimal dominating sets in the n X m king graph.

Original entry on oeis.org

1, 2, 2, 2, 4, 2, 4, 6, 6, 4, 4, 16, 12, 16, 4, 7, 20, 36, 36, 20, 7, 9, 52, 64, 256, 64, 52, 9, 13, 80, 204, 400, 400, 204, 80, 13, 18, 176, 446, 2704, 971, 2704, 446, 176, 18, 25, 296, 1184, 6400, 6486, 6486, 6400, 1184, 296, 25
Offset: 1

Views

Author

Andrew Howroyd, Aug 01 2017

Keywords

Examples

			Array begins:
===========================================================
m\n|  1   2    3     4      5       6        7         8
---|-------------------------------------------------------
1  |  1   2    2     4      4       7        9        13...
2  |  2   4    6    16     20      52       80       176...
3  |  2   6   12    36     64     204      446      1184...
4  |  4  16   36   256    400    2704     6400     30976...
5  |  4  20   64   400    971    6486    22177    112317...
6  |  7  52  204  2704   6486   85405   351503   3082745...
7  |  9  80  446  6400  22177  351503  1997448  21587536...
8  | 13 176 1184 30976 112317 3082745 21587536 360584008...
...
		

Crossrefs

Rows 1-2 are A253413, A286850.
Main diagonal is A286881.
Cf. A218663 (dominating sets), A245013 (independent), A286870 (irredundant).
Cf. A286847 (grid graph).

A253412 Number of n-bit legal binary words with maximal set of 1s.

Original entry on oeis.org

1, 1, 2, 2, 4, 4, 7, 9, 13, 18, 25, 36, 49, 70, 97, 137, 191, 268, 376, 526, 738, 1033, 1449, 2029, 2844, 3985, 5584, 7825, 10964, 15365, 21529, 30169, 42274, 59238, 83008, 116316, 162991, 228393, 320041, 448462, 628417, 880580, 1233929, 1729066, 2422885, 3395113, 4757463
Offset: 0

Views

Author

Steven Finch, Dec 31 2014

Keywords

Comments

An n-bit binary word is legal if every 1 has an adjacent 0.
The set of 1s is maximal if changing any 0 to a 1 makes the word illegal. For example, a maximal word cannot contain 000, 0100, or 0010, and cannot start or end with 00. - Andrew Woods, Jan 02 2015
In other words, the number of minimal dominating sets in the n-path graph P_n. - Eric W. Weisstein, Jul 24 2017

Examples

			The only legal words with maximal set of 1s are:
0 if n = 1;
01 & 10 if n = 2;
010 & 101 if n = 3;
0110, 1001, 0101 & 1010 if n = 4;
01010, 01101, 10101 & 10110 if n = 5; and
010101, 010110, 011001, 011010, 100110, 101010 & 101101 if n = 6.
		

Crossrefs

Asymmetric analog of A000931 (no consecutive 1s but maximal).
Linear analog of A253413.
Cf. A303072.

Programs

  • Mathematica
    LinearRecurrence[{0, 1, 1, 1, 0, -1}, {1, 2, 2, 4, 4, 7}, 50] (* Harvey P. Dale, May 08 2017 *)
    CoefficientList[Series[(1 + 2 x + x^2 + x^3 - x^4 - x^5)/(1 - x^2 - x^3 - x^4 + x^6), {x, 0, 20}], x] (* Eric W. Weisstein, Jul 24 2017 *)
    Table[RootSum[1 - #^2 - #^3 - #^4 + #^6 &, 9 #^n - 18 #^(n + 2) + 23 #^(n + 3) - 3 #^(n + 4) + 32 #^(n + 5) &]/229, {n, 20}] (* Eric W. Weisstein, Aug 04 2017 *)
  • Python
    def A253412(n):
        c, fs = 0, '0'+str(n)+'b'
        for i in range(2**n):
            s = '01'+format(i,fs)+'10'
            for j in range(n):
                if s[j:j+4] == '0100' or s[j+1:j+5] == '0010' or s[j+1:j+4] == '000' or s[j+1:j+4] == '111':
                    break
            else:
                c += 1
        return c # Chai Wah Wu, Jan 02 2015

Formula

a(n) = a(n-2) + a(n-3) + a(n-4) - a(n-6), for n >= 6, with a(0) = a(1) = 1, a(2) = a(3) = 2, a(4) = a(5) = 4, a(6) = 7. - Andrew Woods, Jan 02 2015
G.f.: (1 + x^2)*(1 + x -x^3) / (1 - x^2 - x^3 - x^4 + x^6). - Paul D. Hanna, Jan 02 2015
a(n) = sqrt(A303072(n)). - Eric W. Weisstein, Apr 18 2018

Extensions

Terms a(21) and beyond from Andrew Woods, Jan 02 2015
a(0)=1 prepended by Alois P. Heinz, Oct 26 2022

A300738 Number of minimal total dominating sets in the n-cycle graph.

Original entry on oeis.org

0, 0, 3, 4, 5, 9, 7, 4, 12, 25, 22, 25, 39, 49, 68, 100, 119, 144, 209, 289, 367, 484, 644, 841, 1130, 1521, 1983, 2601, 3480, 4624, 6107, 8100, 10717, 14161, 18807, 24964, 33004, 43681, 57918, 76729, 101639, 134689, 178364, 236196, 313007, 414736, 549289
Offset: 1

Views

Author

Andrew Howroyd, Apr 15 2018

Keywords

Crossrefs

Cf. A001608, A001638 (total dominating sets), A253413, A302653, A302655, A302918.

Programs

  • Mathematica
    Table[RootSum[-1 - # + #^3 &, #^n &] + (1 + (-1)^n) RootSum[-1 + #^2 + #^3 &, #^(n/2) &], {n, 20}]
    Perrin[n_] := RootSum[-1 - # + #^3 &, #^n &]; Table[With[{b = Mod[n, 2, 1]}, Perrin[n/b]^b], {n, 20}]
    LinearRecurrence[{0, 0, 1, 1, 1, 1, 0, -1, -1}, {0, 0, 3, 4, 5, 9, 7, 4, 12}, 20]
    CoefficientList[Series[x^2 (3 + 4 x + 5 x^2 + 6 x^3 - 8 x^5 - 9 x^6)/(1 - x^3 - x^4 - x^5 - x^6 + x^8 + x^9), {x, 0, 20}], x]
  • PARI
    concat([0,0], Vec((3 + 4*x + 5*x^2 + 6*x^3 - 8*x^5 - 9*x^6)/((1 - x^2 - x^3)*(1 + x^2 - x^6)) + O(x^50)))

Formula

a(n) = a(n-3) + a(n-4) + a(n-5) + a(n-6) - a(n-8) - a(n-9) for n > 9.
G.f.: x^3*(3 + 4*x + 5*x^2 + 6*x^3 - 8*x^5 - 9*x^6)/((1 - x^2 - x^3)*(1 + x^2 - x^6)).
a(2*n) = A001608(n)^2.
a(2*n-1) = A001608(2*n-1), where A001608 are the Perrin numbers.

A290270 Number of minimal dominating sets in the n-wheel graph.

Original entry on oeis.org

3, 4, 7, 6, 6, 15, 15, 22, 28, 45, 58, 79, 115, 159, 223, 307, 438, 609, 852, 1194, 1675, 2347, 3282, 4606, 6451, 9040, 12663, 17749, 24871, 34845, 48831, 68424, 95883, 134350, 188266, 263811, 369667, 518002, 725860, 1017129, 1425262, 1997179, 2798583
Offset: 3

Views

Author

Eric W. Weisstein, Jul 25 2017

Keywords

Comments

The n-wheel graph is well defined for n >= 4. If the sequence is extended to n=1 using A253413 then the initial terms are 1,2,3,4,... If the sequence is extended using the recurrence the initial terms are 7,1,3,4,... - Andrew Howroyd, Jul 27 2017

Crossrefs

Cf. A253413.

Programs

  • Magma
    I:=[3,4,7,6,6,15,15,22,28]; [n le 9 select I[n] else Self(n-2)+Self(n-3)+Self(n-4)-Self(n-6)-1: n in [1..50]]; // Vincenzo Librandi, Aug 04 2017
  • Mathematica
    Table[1 + RootSum[1 - #1^2 - #1^3 - #1^4 + #1^6 &, #^(n - 1) &], {n, 3, 20}] (* Eric W. Weisstein, Aug 04 2017 *)
    LinearRecurrence[{1, 1, 0, 0, -1, -1, 1}, {3, 4, 7, 6, 6, 15, 15}, 20] (* Eric W. Weisstein, Aug 04 2017 *)
    CoefficientList[Series[(3 + x - 5 x^3 - 7 x^4 + 6 x^5 + x^6)/((1 - x^2 - x^3 - x^4 + x^6) (1-x)), {x, 0,33}], x] (* Vincenzo Librandi, Aug 04 2017 *)
  • PARI
    Vec(((7-6*x-5*x^2+2*x^5+x^6)) / ((1-x^2-x^3-x^4+x^6)*(1-x)) + O(x^40)) \\ Andrew Howroyd, Jul 27 2017
    

Formula

From Andrew Howroyd, Jul 27 2017: (Start)
a(n) = A253413(n-1) + 1 for n > 2.
a(n) = a(n-2) + a(n-3) + a(n-4) - a(n-6) - 1 for n>8.
G.f.: x*(7 - 6*x - 5*x^2 + 2*x^5 + x^6) / ((1 - x^2 - x^3 -x^4 + x^6)*(1 - x)).
(End)
G.f.: x^3*(3+x-5*x^3-7*x^4+6*x^5+x^6)/((1-x^2-x^3-x^4+x^6)*(1-x)). - Vincenzo Librandi, Aug 04 2017

Extensions

a(3) and a(16)-a(45) from Andrew Howroyd, Jul 27 2017

A347638 Number of minimal dominating sets in the n-dipyramidal graph (for n > 3).

Original entry on oeis.org

3, 7, 10, 15, 16, 18, 29, 31, 40, 48, 67, 82, 105, 143, 189, 255, 341, 474, 647, 892, 1236, 1719, 2393, 3330, 4656, 6503, 9094, 12719, 17807, 24931, 34907, 48895, 68490, 95951, 134420, 188338, 263885, 369743, 518080, 725940, 1017211, 1425346, 1997265, 2798671
Offset: 1

Views

Author

Eric W. Weisstein, Sep 09 2021

Keywords

Comments

The 3-dipyramidal graph deviates from this sequence because it has 4 minimal dominating sets while a(3) = 10.

Crossrefs

Cf. A253413.

Programs

  • Mathematica
    Table[2 n + 1 + RootSum[1 - #^2 - #^3 - #^4 + #^6 &, #^n &], {n, 20}]
    LinearRecurrence[{2, 0, -1, 0, -1, 0, 2, -1}, {3, 7, 10, 15, 16, 18, 29, 31}, 20]
    CoefficientList[Series[(3 + x - 4 x^2 - 2 x^3 - 7 x^4 - x^5 + 15 x^6 - 7 x^7)/((-1 + x)^2 (1 - x^2 - x^3 - x^4 + x^6)), {x, 0, 20}], x]

Formula

a(n) = A253413(n)+2*n+1.
a(n) = 2*a(n-1)-a(n-3)-a(n-5)+2*a(n-7)-a(n-8).
G.f.: x*(3+x-4*x^2-2*x^3-7*x^4-x^5+15*x^6-7*x^7)/((-1+x)^2*(1-x^2-x^3-x^4+x^6)).
Showing 1-5 of 5 results.