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.

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A058527 Number of 2n X 2n 0-1 matrices with n ones in each row and each column.

Original entry on oeis.org

1, 2, 90, 297200, 116963796250, 6736218287430460752, 64051375889927380035549804336, 108738182111446498614705217754614976371200, 34812290428176298285394893936773707951192224124239796250, 2188263032066768922535710968724036448759525154977348944382853301460850000
Offset: 0

Views

Author

David desJardins, Dec 22 2000

Keywords

Crossrefs

Central coefficients of A008300.
Main diagonal of A376935.

Extensions

More terms (using dynamic programming in Python) from Greg Kuperberg, Feb 08 2001
More terms from Vladeta Jovovic, Nov 12 2006

A174580 Let J_n be an n X n matrix which contains 1's only, I = I_n be the n X n identity matrix, and P = P_n be the incidence matrix of the cycle (1,2,3,...,n). Then a(n) is the number of (0,1,2) n X n matrices A <= 2(J_n - I - P) with exactly one 1 and one 2 in every row and column.

Original entry on oeis.org

0, 2, 36, 1462, 83600, 5955474
Offset: 3

Views

Author

Vladimir Shevelev, Mar 23 2010

Keywords

References

  • V. S. Shevelev, Development of the rook technique for calculating the cyclic indicators of (0,1)-matrices, Izvestia Vuzov of the North-Caucasus region, Nature sciences 4 (1996), 21-28 (in Russian).
  • S. E. Grigorchuk, V. S. Shevelev, An algorithm of computing the cyclic indicator of couples discordant permutations with restricted position, Izvestia Vuzov of the North-Caucasus region, Nature sciences 3 (1997), 5-13 (in Russian).

Crossrefs

A174581 Let J_n be an n X n all-1's matrix, I = I_n the n X n identity matrix and P = P_n the incidence matrix of the cycle (1,2,3,...,n). Then a(n) is the number of (0,1) n X n matrices A <= J_n - I - P - P^2 with exactly two 1's in every row and column.

Original entry on oeis.org

0, 1, 20, 1266, 102574, 9746472
Offset: 4

Views

Author

Vladimir Shevelev, Mar 23 2010

Keywords

References

  • V. S. Shevelev, Development of the rook technique for calculating the cyclic indicators of (0,1)-matrices, Izvestia Vuzov of the North-Caucasus region, Nature sciences 4 (1996), 21-28 (in Russian).
  • S. E. Grigorchuk, V. S. Shevelev, An algorithm of computing the cyclic indicator of couples discordant permutations with restricted position, Izvestia Vuzov of the North-Caucasus region, Nature sciences 3 (1997), 5-13 (in Russian).

Crossrefs

A174586 Number of n X n (0,1) matrices with two 1's in each row having positive permanent.

Original entry on oeis.org

0, 1, 24, 954, 59040, 5295150, 651354480, 105393619800, 21717404916480, 5554438422838200, 1726882980691176000, 641506478978753110800, 280659563041747649760000, 142843312073975729801785200, 83684308104396267184700784000, 55915646244745131440225950320000
Offset: 1

Views

Author

Vladimir Shevelev, Mar 23 2010

Keywords

Comments

a(n) is the normalized volume of the convex hull of (classical) parking functions of length n. - Andrés R. Vindas-Meléndez, Jan 13 2023

References

  • Vladimir Shevelev, On the permanent of the stochastic (0,1)-matrices with equal row sums, Izvestia Vuzov of the North-Caucasus region, Nature sciences 1 (1997), 21-38 (in Russian).

Crossrefs

Programs

  • Mathematica
    Table[n!/2^n * Sum[(2*i-1)*(2*i-1)!!*Binomial[n,i]*(2n-1)^(n-i-1),{i,0,n}],{n,1,20}] (* Vaclav Kotesovec, Nov 30 2017 *)

Formula

a(2)=1, for n>=3, a(n) = A001499(n) + Sum_{k=1..n-2} (-1)^(k+1)*k!*(C(n,k))^2*(n-k)^k*a(n-k).
a(n) = n!*((n-1)/2^(n-1))*Sum_{i=0..n-2} (2i+1)!!*C(n-2,i)*(2n-1)^(n-i-2). [corrected by John Lentfer, Oct 05 2022]
For n>=2, a(n) = (n!/2^n)*Sum_{i=0..n} (2i-1)*(2i-1)!!*C(n,i)*(2n-1)^(n-i-1).
a(n) = Gamma(3/4)*(sqrt(2)*Pi*e)^(-1/2)*n!*n^(n-1/4)*(1+O(n^((-1/4)+epsilon) with arbitrary small epsilon>0 for sufficiently large n.

A066300 Number of n X n matrices with exactly 2 1's in each row, other entries 0.

Original entry on oeis.org

0, 1, 27, 1296, 100000, 11390625, 1801088541, 377801998336, 101559956668416, 34050628916015625, 13931233916552734375, 6831675453247426400256, 3955759092264800909058048, 2670419511272061205254504361
Offset: 1

Views

Author

Sharon Sela (sharonsela(AT)hotmail.com), Jan 01 2002

Keywords

Crossrefs

Cf. A001499.

Programs

  • Mathematica
    Table[ Binomial[n, 2]^n, {n, 1, 16} ]
  • PARI
    a(n) = binomial(n,2)^n \\ Charles R Greathouse IV, Dec 16 2016

Formula

a(n) = binomial(n,2)^n.

Extensions

More terms from Robert G. Wilson v, Jan 03 2002

A112579 Number of 3-D arrays of 0's and 1's with plane sums 2.

Original entry on oeis.org

0, 8, 900, 366336, 378028800, 833156928000, 3477528928742400, 25183876050321408000, 296058177312000019660800, 5362158372805111867637760000, 143458227395428379364635443200000
Offset: 1

Views

Author

Peter J. Cameron, Sep 14 2005

Keywords

Examples

			a(2)=8: six pairs of opposite edges and two inscribed tetrahedra.
		

References

  • P. J. Cameron and T. W. Mueller, Decomposable functors and the exponential principle, II, in preparation

Crossrefs

Cf. A001499 (2-D case), A112578, A112580.

Formula

a(n) = b(n) + Sum (k/n)*(n choose k)^3*b(k)*a(n-k), where b(n) counts indecomposable arrays (A112578).

A112580 Number of 3-D arrays of nonnegative integers with plane sums 2.

Original entry on oeis.org

1, 12, 1152, 431424, 427723200, 920031955200, 3777894212198400, 27039993414897254400, 315084437077115278540800, 5667616936309704095784960000, 150796432741520745587273564160000
Offset: 1

Views

Author

Peter J. Cameron, Sep 14 2005

Keywords

Examples

			a(2)=12: eight 0-1 arrays and four with 2s at opposite vertices.
		

References

  • P. J. Cameron and T. W. Mueller, Decomposable functors and the exponential principle, II, in preparation

Crossrefs

Cf. A001499 (2-D case), A112578, A112579.

Formula

a(n) = b(n) + Sum (k/n)*(n choose k)^3*b(k)*a(n-k), where b(n) counts indecomposable arrays (A112578 with first term 1).

A174582 Let J_n be n X n matrix which contains 1's only, I=I_n be the n X n identity matrix and P=P_n be the incidence matrix of the cycle (1,2,3,...,n). Then a(n) is the number of (0,1,2) n X n matrices A<=2(J_n-I-P-P^2) with exactly one 1 and one 2 in every row and column.

Original entry on oeis.org

0, 2, 72, 3722, 329192, 32842446
Offset: 4

Views

Author

Vladimir Shevelev, Mar 23 2010

Keywords

References

  • V. S. Shevelev, Development of the rook technique for calculating the cyclic indicators of (0,1)-matrices, Izvestia Vuzov of the North-Caucasus region, Nature sciences 4 (1996), 21-28 (in Russian).
  • S. E. Grigorchuk, V. S. Shevelev, An algorithm of computing the cyclic indicator of couples discordant permutations with restricted position, Izvestia Vuzov of the North-Caucasus region, Nature sciences 3 (1997), 5-13 (in Russian).

Crossrefs

A225623 Number of ways to arrange 2n queens on an n X n chessboard, with no more than 2 queens in each row, column or diagonal.

Original entry on oeis.org

0, 1, 2, 11, 92, 1097, 19448, 477136, 14244856, 537809179, 24194010708, 1317062528249
Offset: 1

Views

Author

Vaclav Kotesovec, Aug 04 2013

Keywords

Comments

This problem is slightly different from A000769 or A219760. In the first example on an 8 x 8 board, the queens c7, d5 and e3 (or queens a2, c5 and e8) are in a line, but such case is allowed. The elementary step can be only [0,1], [1,0] or [1,1], not for example [1,2] or [2,3].

Crossrefs

Extensions

Definition clarified by Vaclav Kotesovec, Dec 18 2014
a(10)-a(12) from Martin Ehrenstein, Jan 09 2022

A156430 Number of n X n arrays of squares of integers, symmetric about both diagonal and antidiagonal, with all rows summing to 2.

Original entry on oeis.org

1, 2, 10, 12, 84, 132, 954, 1728, 13290, 26820, 217500, 481320, 4086600, 9783480, 86549820, 221921280, 2037627900, 5552479800, 52745205240, 151802154000, 1487961422640, 4500041903280, 45412066438200, 143712079822080, 1490217165997560, 4917227802767280
Offset: 2

Views

Author

R. H. Hardin, Feb 09 2009

Keywords

Crossrefs

Programs

  • Python
    # Even-dim bisymmetric
    A = [1, 1, 10]
    B = [0, 2, 6]
    C = [0, 1, 6]
    for n in range(3, 13):
        a_next = A[-1] + (n-1)*A[-2] + 4*(n-1)*B[-1] + 2*(n-1)*(n-2)*C[-1]
        b_next = 2*A[-1] + 2*(n-1)*B[-1]
        c_next = 4*B[-1] - 2*A[-2] + 4*(n-2)*A[-3] + 4*(n-2)*(n-3)*C[-2]
        A.append(a_next)
        B.append(b_next)
        C.append(c_next)
    # Odd-dim bisymmetric
    A_odd = [B[n]*n for n in range(len(B))]
    # Albert Zhou, Jan 26 2025

Formula

From Albert Zhou, Jan 26 2025: (Start)
a(2*n) = a(2*(n-1)) + (n-1)*a(2*(n-2)) + 4*(n-1)*b(2*(n-1)) + 2*(n-1)*(n-2)*c(2*(n-1)), where
b(2*n) = 2*a(2*(n-1)) + 2*(n-1)*b(2*(n-1)), and
c(2*n) = 4*b(2*(n-1)) - 2*a(2*(n-2)) + 4*(n-2)*a(2*(n-3)) + 4*(n-2)*(n-3)*c(2*(n-2)), with
a(0) = 1, a(2) = 1, a(4) = 10, and
b(0) = 0, b(2) = 2, b(4) = 6, and
c(0) = 0, c(2) = 1, c(6) = 6.
a(2*n+1) = n*b(2*n).
Proof attached. (End)

Extensions

a(26)-a(27) from Albert Zhou, Jan 26 2025
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