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.

A185178 Number of distinct values of the permanent of an n X n (0,1)-matrix with exactly three 1's in each row and each column.

Original entry on oeis.org

1, 1, 2, 4, 8, 18, 32, 61, 109
Offset: 3

Views

Author

Vladimir Shevelev, Feb 19 2011

Keywords

Comments

The values a(n) are unknown for n>=9.
a(12) >= 170, a(13) >= 276, a(14) >= 438, a(15) >= 547. - Robert P. P. McKone, Jul 14 2025

References

  • V. I. Bolshakov, On spectrum of permanent on Lambda_n^k, Proc. of Seminar on Discrete Math. and Appl., Moscow State Univ. (1986), 65-73 (in Russian).

Crossrefs

Cf. A185179 (values of the permanent), A176211, A176212.
Cf. A001501 (number of n X n (0,1)-matrix with exactly three 1's in each row and each column).

Extensions

a(9)-a(11) from Robert P. P. McKone, Jul 22 2025

A176211 Numbers of the form Product_{m_i >= 3} A000211(m_i), possibly repeated, in natural order.

Original entry on oeis.org

6, 9, 13, 20, 31, 36, 49, 54, 78, 78, 81, 117, 120, 125, 169, 180, 186, 201, 216, 260, 279, 294, 324, 324, 400, 403, 441, 468, 468, 486, 523, 620, 637, 702, 702, 720, 729, 750, 845, 961, 980, 1014, 1014, 1053, 1080, 1116, 1125, 1206, 1296, 1366, 1519, 1521, 1560, 1560, 1620, 1625, 1674, 1764, 1809, 1944, 1944, 2197, 2209
Offset: 1

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Author

Vladimir Shevelev, Apr 12 2010

Keywords

Comments

Values represented by more than one set of indices are listed once per set; otherwise A176212 results.
Each term is a permanent of a quadratic symmetric (0,1) matrix with 1's on the main diagonal and exactly three 1's in each row and column.
For fixed Sum m_i=n with m_i >= 3, Product A000211(m_i) >= 6(4/3)^(n-3) and max(Product A000211(m_i)) = 6^((n-h)/3)*floor((3/2)^h), where h is the remainder of n (mod 3).

Crossrefs

Programs

  • PARI
    f(n) = fibonacci(n+1) + fibonacci(n-1) + 2; \\ A000211
    lista(nn) = {my(v = vector(nn, k, f(k+2))); my(vmax = vecmax(v)); my(w =  vector(nn, k, [0, logint(vmax, v[k])])); my(list=List()); forvec(x = w, if (vecmax(x), my(y = prod(k=1, #v, v[k]^x[k])); if (y <= vmax, listput(list, y)););); Vec(vecsort(list));}
    lista(14) \\ Michel Marcus, Jan 06 2021

A185179 Irregular triangle, read by rows, of the A185178(n) values of the permanent of an n X n (0,1)-matrix (n>=3) with exactly three 1's in each row and each column.

Original entry on oeis.org

6, 9, 12, 13, 17, 18, 20, 36, 24, 25, 26, 27, 30, 31, 32, 54, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 44, 45, 48, 49, 52, 72, 78, 81, 42, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 62, 63, 64, 66, 68, 70, 72, 78, 84, 102, 108, 117, 120, 216
Offset: 3

Views

Author

Vladimir Shevelev, Feb 19 2011

Keywords

Examples

			Triangle begins:
  6
  9
  12, 13
  17, 18, 20, 36
  24, 25, 26, 27, 30, 31, 32, 54
  33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 44, 45, 48, 49, 52, 72, 78, 81
  42, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 62, 63, 64, 66, 68, 70, 72, 78, 84, 102, 108, 117, 120, 216
		

References

  • V. I. Bolshakov, On spectrum of permanent on Lambda_n^k, Proc. of Seminar on Discrete Math. and Appl., Moscow State Univ. (1986), 65-73 (in Russian).

Crossrefs

Extensions

More terms from Robert P. P. McKone, Jul 26 2025

A185177 Different values of the permanent in (0,1) quadratic matrices with exactly 3 ones in each row and each column, in the increasing order.

Original entry on oeis.org

6, 9, 12, 13, 17, 18, 20, 24, 25, 26, 27, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42
Offset: 1

Views

Author

Vladimir Shevelev, Feb 19 2011

Keywords

Comments

The sequence contains all different terms of A185179 in increasing order.

References

  • V. I. Bolshakov, On spectrum of permanent on Lambda_n^k, Proc. of Seminar on Discrete Math. and Appl., Moscow State Univ. (1986), 65-73 (in Russian).

Crossrefs

A232553 Maximal values of permanent on (0,1) square matrices of order n with row and column sums 3.

Original entry on oeis.org

6, 9, 13, 36, 54, 81, 216, 324, 486, 1296, 1944, 2916, 7776, 11664, 17496, 46656, 69984, 104976, 279936, 419904, 629856, 1679616, 2519424, 3779136, 10077696, 15116544, 22674816, 60466176, 90699264, 136048896, 362797056, 544195584, 816293376, 2176782336, 3265173504, 4897760256
Offset: 3

Views

Author

Vladimir Shevelev, Nov 26 2013

Keywords

Comments

a(n) is attained on the subset of symmetric matrices with the main diagonal all 1's.

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{0, 0, 6}, {6, 9, 13, 36, 54, 81}, 50] (* Paolo Xausa, Aug 08 2025 *)
  • PARI
    a(n) = h = n%3; floor(6^((n-h)/3)*(3/2)^h); \\ Michel Marcus, Nov 26 2013
    
  • PARI
    Vec(x^3*(6+9*x+13*x^2+3*x^5)/(1-6*x^3) + O(x^50)) \\ Colin Barker, May 27 2016

Formula

a(n) = floor(6^((n-h)/3)*(3/2)^h), where h=0,1 or 2, such that n == h (mod 3).
From Colin Barker, May 27 2016: (Start)
a(n) = 6*a(n-3) for n>8. [Corrected by Paolo Xausa, Aug 08 2025]
G.f.: x^3*(6+9*x+13*x^2+3*x^5) / (1-6*x^3). (End)

A232636 The second largest value of permanent of (0,1) square matrices of order n with row and column sums equal to 3.

Original entry on oeis.org

34012224, 53747712, 131010048, 204073344, 322486272, 786060288, 1224440064, 1934917632, 4716361728, 7346640384, 11609505792, 28298170368, 44079842304, 69657034752, 169789022208, 264479053824, 417942208512
Offset: 30

Views

Author

Vladimir Shevelev, Nov 27 2013

Keywords

Comments

The interval (a(n), A232553(n)) contains no permanents of the matrices under consideration. For n=3 and n=4, the permanent takes only one value: 6 and 9 respectively. Our method (see Shevelev link) allows us to find a simple regularity of the sequence only beginning with n=30 (see formula). However, several values for 5<=n<30 are known: a(5)=13, a(6)=20, a(7)=32, a(8)=78, a(9)=120, a(12)=729, a(15)=4374, a(18)=26244, a(21)=157464, a(24)=944784, a(27)=5668704 (Bolshakov) and a(28)=8957952.
We conjecture that formula below also holds for other values.
In cases n==0 (nod 3), n>=6, and n==2 (mod 3), at least, for n=8 and n>=32, the second largest value of permanent attains on subset of symmetric matrices with the main diagonal of 1's, and does not attain, if n==1 (mod 3), at least, for n=7 and n>=28.
All terms for n>30 not divisible by 3 are conjectural since our method is based on the following very plausible but yet not proved conjecture with confirms in many cases and without counterexample since 1992 (when it was posed, see ref. [11] in Shevelev link). Let L_n be the set of considered n X n (0,1)-matrices with all row and column sums equal to 3. Let S_n be the subset of completely indecomposable such matrices, i.e., not containing submatrices from L_m (m

References

  • V. I. Bolshakov, On spectrum of permanent on Lambda_n^k, Proc. of Seminar on Discrete Math. and Appl., Moscow State Univ. (1986), 65-73 (in Russian).

Formula

a(n) = 9/16 * 6^(n/3), if n>=12, n==0 (mod 3) (Bolshakov); a(n) = 8/9 * 6^((n-1)/3), if n>=28, n== 1 (mod 3); a(n) = 13/6 * 6^((n-2)/3), if n>=32, n==2 (mod 3).
Conjectures from Colin Barker, May 27 2016: (Start)
a(n) = 6*a(n-3) for n>32.
G.f.: 419904*x^30*(81+128*x+312*x^2) / (1-6*x^3).
(End)

Extensions

Edited by M. F. Hasler, Nov 30 2013
Showing 1-6 of 6 results.