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 1-9 of 9 results.

A221438 T(n,k) is the number of n X k 1..(max n,k) arrays with each row and column having unrepeated values.

Original entry on oeis.org

1, 2, 2, 6, 2, 6, 24, 12, 12, 24, 120, 216, 12, 216, 120, 720, 5280, 576, 576, 5280, 720, 5040, 190800, 66240, 576, 66240, 190800, 5040, 40320, 9344160, 15321600, 161280, 161280, 15321600, 9344160, 40320, 362880, 598066560, 5411750400, 283046400
Offset: 1

Views

Author

R. H. Hardin, Jan 16 2013

Keywords

Comments

Table starts:
....1.......2..........6...........24............120............720
....2.......2.........12..........216...........5280.........190800
....6......12.........12..........576..........66240.......15321600
...24.....216........576..........576.........161280......283046400
..120....5280......66240.......161280.........161280......812851200
..720..190800...15321600....283046400......812851200......812851200
.5040.9344160.5411750400.782137036800.20449013760000.61479419904000

Examples

			Some solutions for n=3 and k=4:
..4..1..3..2....3..1..4..2....1..2..4..3....3..4..2..1....2..3..4..1
..2..3..4..1....1..3..2..4....3..4..1..2....1..2..3..4....1..4..3..2
..1..4..2..3....2..4..3..1....2..1..3..4....2..1..4..3....3..2..1..4
		

Crossrefs

Diagonal is A002860.
Column 1 is A000142.
Column 2 is A082491.

A174564 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 (2,3,...,n,1). Then a(n) is the number of (0,1) n X n matrices A<=J_n-I-P with exactly two 1's in every row and column.

Original entry on oeis.org

0, 1, 13, 522, 27828, 1867363
Offset: 3

Views

Author

Vladimir Shevelev, Mar 22 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

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.

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

A174584 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) n X n matrices A<=J_n-I-P-P^2-P^3 with exactly two 1's in every row and column.

Original entry on oeis.org

0, 1, 31, 3114, 381022
Offset: 5

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

A346409 a(n) = (n!)^2 * Sum_{k=0..n-1} (-1)^k / ((n-k)^2 * k!).

Original entry on oeis.org

0, 1, -3, 13, -52, 476, 1344, 156192, 6935424, 470168064, 38948065920, 3979380286080, 489922581219840, 71586095491054080, 12249193741572372480, 2426646293132502067200, 551096248249459158220800, 142236660450422499604070400, 41404182857569072540171468800
Offset: 0

Views

Author

Ilya Gutkovskiy, Jul 15 2021

Keywords

Crossrefs

Programs

  • Mathematica
    Table[(n!)^2 Sum[(-1)^k/((n - k)^2 k!), {k, 0, n - 1}], {n, 0, 18}]
    nmax = 18; CoefficientList[Series[PolyLog[2, x] Exp[-x], {x, 0, nmax}], x] Range[0, nmax]!^2

Formula

Sum_{n>=0} a(n) * x^n / (n!)^2 = polylog(2,x) * exp(-x).

A174585 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-P^3) with exactly one 1 and one 2 in every row and column.

Original entry on oeis.org

0, 2, 132, 9800, 1309928
Offset: 5

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

Showing 1-9 of 9 results.