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.

A215297 T(n,k) = number of permutations of 0..floor((n*k-2)/2) on odd squares of an n X k array such that each row and column of odd squares is increasing.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 3, 1, 1, 6, 6, 6, 1, 1, 10, 30, 30, 10, 1, 1, 20, 70, 280, 70, 20, 1, 1, 35, 420, 2100, 2100, 420, 35, 1, 1, 70, 1050, 23100, 23100, 23100, 1050, 70, 1, 1, 126, 6930, 210210, 1051050, 1051050, 210210, 6930, 126, 1, 1, 252, 18018, 2522520, 14294280
Offset: 1

Views

Author

R. H. Hardin, Aug 07 2012

Keywords

Comments

Table starts
.1...1.....1........1...........1..............1.................1
.1...2.....3........6..........10.............20................35
.1...3.....6.......30..........70............420..............1050
.1...6....30......280........2100..........23100............210210
.1..10....70.....2100.......23100........1051050..........14294280
.1..20...420....23100.....1051050.......85765680........5703417720
.1..35..1050...210210....14294280.....5703417720......577185873264
.1..70..6930..2522520...814773960...577185873264...337653735859440
.1.126.18018.25729704.12547518984.48236247979920.43364386933948080
Even columns match A215292.
The first column is number of symmetric standard Young tableaux of shape (n), the second column is number of symmetric standard Young tableaux of shape (n,n) and the third column is number of symmetric standard Young tableaux of shape (n,n,n). - Ran Pan, May 21 2015

Examples

			Some solutions for n=5, k=4:
..x..0..x..4....x..0..x..1....x..1..x..3....x..0..x..6....x..0..x..1
..1..x..2..x....4..x..7..x....0..x..8..x....3..x..5..x....3..x..7..x
..x..3..x..8....x..2..x..3....x..2..x..5....x..1..x..7....x..2..x..5
..6..x..7..x....5..x..9..x....4..x..9..x....4..x..9..x....6..x..8..x
..x..5..x..9....x..6..x..8....x..6..x..7....x..2..x..8....x..4..x..9
		

Crossrefs

Column 2 is A001405. Column 4 is A215288. Column 6 is A215290.

Formula

f1=floor(k/2), f2=floor((k+1)/2), f3=floor((n+1)/2), f4=floor(n/2);
T(n,k) = A060854(f1,f3)*A060854(f2,f4)*binomial(f1*f3+f2*f4,f1*f3).

A215288 Number of permutations of 0..floor((n*4-1)/2) on even squares of an n X 4 array such that each row and column of even squares is increasing.

Original entry on oeis.org

1, 6, 30, 280, 2100, 23100, 210210, 2522520, 25729704, 325909584, 3585005424, 47117214144, 546896235600, 7383099180600, 89212448432250, 1229149289511000, 15323394475903800, 214527522662653200, 2742051789669912720
Offset: 1

Views

Author

R. H. Hardin, Aug 07 2012

Keywords

Examples

			Some solutions for n=5
..2..x..4..x....0..x..3..x....2..x..3..x....0..x..5..x....1..x..4..x
..x..0..x..1....x..2..x..5....x..0..x..4....x..1..x..3....x..0..x..6
..3..x..7..x....1..x..6..x....5..x..6..x....6..x..7..x....2..x..5..x
..x..6..x..9....x..4..x..7....x..1..x..8....x..2..x..4....x..3..x..8
..5..x..8..x....8..x..9..x....7..x..9..x....8..x..9..x....7..x..9..x
		

Crossrefs

Column 4 of A215292.

Formula

f3=floor((n+1)/2),
f4=floor(n/2),
a(n) = A060854(2,f3)*A060854(2,f4)*binomial(2*f3+2*f4,2*f3).

A215287 Number of permutations of 0..floor((n*3-1)/2) on even squares of an n X 3 array such that each row and column of even squares is increasing.

Original entry on oeis.org

1, 3, 10, 30, 140, 420, 2310, 6930, 42042, 126126, 816816, 2450448, 16628040, 49884120, 350574510, 1051723530, 7595781050, 22787343150, 168212023980, 504636071940, 3792416540640, 11377249621920, 86787993910800, 260363981732400, 2011383287449200
Offset: 1

Views

Author

R. H. Hardin, Aug 07 2012

Keywords

Comments

Also Schröder paths of length n having floor(n/2) peaks. - Peter Luschny, Sep 30 2018

Examples

			Some solutions for n=5:
  0 x 4   0 x 5   1 x 3   0 x 1   0 x 3   1 x 4   0 x 2
  x 3 x   x 1 x   x 0 x   x 4 x   x 2 x   x 0 x   x 1 x
  1 x 5   2 x 6   2 x 5   2 x 3   1 x 6   2 x 5   3 x 5
  x 7 x   x 3 x   x 6 x   x 6 x   x 5 x   x 6 x   x 6 x
  2 x 6   4 x 7   4 x 7   5 x 7   4 x 7   3 x 7   4 x 7
		

Crossrefs

Column 3 of A215292.

Programs

  • Magma
    [(n-(n div 2)+1)*Factorial(2*n-(n div 2)) / (Factorial(n-(n div 2) +1)^2*Factorial((n div 2))): n in [1..30]]; // Vincenzo Librandi, Oct 01 2018
  • Maple
    T := (n, k) -> (n-k+1)*(2*n-k)!/((n-k+1)!^2*k!):
    a := n -> T(n, floor(n/2)): seq(a(n), n = 1..23); # Peter Luschny, Sep 30 2018
  • Mathematica
    Table[(n - Floor[n/2] + 1) (2 n - Floor[n/2])! / ((n -Floor[n/2] + 1)!^2 Floor[n/2]!), {n, 1, 30}] (* Vincenzo Librandi, Oct 01 2018 *)

Formula

f3 = floor((n+1)/2); f4 = floor(n/2);
a(n) = A060854(2,f3)*A060854(1,f4)*binomial(2*f3+1*f4,2*f3).
a(n) = (n - f + 1)*(2*n - f)! / ((n - f + 1)!^2 * f!) where f = floor(n/2). - Peter Luschny, Sep 30 2018

A215290 Number of permutations of 0..floor((n*6-1)/2) on even squares of an nX6 array such that each row and column of even squares is increasing.

Original entry on oeis.org

1, 20, 420, 23100, 1051050, 85765680, 5703417720, 577185873264, 48236247979920, 5595404765670720, 545152292883918720, 69506917342699636800, 7562187114225380722800, 1033498905610802032116000
Offset: 1

Views

Author

R. H. Hardin Aug 07 2012

Keywords

Comments

Column 6 of A215292

Examples

			Some solutions for n=4
..0..x..2..x..6..x....1..x..6..x..7..x....1..x..2..x..7..x....0..x..2..x..6..x
..x..1..x..3..x..5....x..0..x..2..x..4....x..0..x..4..x.10....x..3..x..5..x..7
..4..x..9..x.10..x....9..x.10..x.11..x....3..x..6..x..8..x....1..x..9..x.11..x
..x..7..x..8..x.11....x..3..x..5..x..8....x..5..x..9..x.11....x..4..x..8..x.10
		

Formula

f3=floor((n+1)/2)
f4=floor(n/2)
a(n) = A060854(3,f3)*A060854(3,f4)*binomial(3*f3+3*f4,3*f3)

A215286 Number of permutations of 0..floor((n*n-1)/2) on even squares of an n X n array such that each row and column of even squares is increasing.

Original entry on oeis.org

1, 2, 10, 280, 60060, 85765680, 2061378118800, 346915095471584640, 1736278161426147413954880, 62144711688730139887005809020800, 103104526145243794108489566205445861006400
Offset: 1

Views

Author

R. H. Hardin, Aug 07 2012

Keywords

Comments

Diagonal of A215292.

Examples

			Some solutions for n=5
..0..x..1..x..2....0..x..2..x..6....0..x..2..x..4....1..x..2..x..6
..x..4..x..7..x....x..1..x..3..x....x..3..x..5..x....x..0..x..8..x
..3..x..6..x..9....5..x..8..x.11....1..x..8..x..9....3..x..5..x.10
..x..5..x.11..x....x..4..x..9..x....x..7..x.10..x....x..9..x.12..x
..8..x.10..x.12....7..x.10..x.12....6..x.11..x.12....4..x..7..x.11
		

Crossrefs

Formula

f1 = floor((n+1)/2)
f2 = floor(n/2)
T(n,k) = A060854(f1,f1)*A060854(f2,f2)*binomial(f1*f1+f2*f2,f1*f1).

A215289 Number of permutations of 0..floor((n*5-1)/2) on even squares of an n X 5 array such that each row and column of even squares is increasing.

Original entry on oeis.org

1, 10, 140, 2100, 60060, 1051050, 42882840, 814773960, 41227562376, 824551247520, 48236247979920, 999179422441200, 64899082486180800, 1379105502831342000, 96951116849043342600, 2100607531729272423000, 157112712418611824074200, 3456479673209460129632400, 271742147399231010918736320
Offset: 1

Views

Author

R. H. Hardin, Aug 07 2012

Keywords

Examples

			Some solutions for n=5:
..0..x..2..x..6....1..x..2..x..6....0..x..3..x..9....0..x..1..x..8
..x..3..x..4..x....x..0..x..4..x....x..2..x..4..x....x..3..x..6..x
..1..x..7..x.10....7..x..9..x.11....1..x..7..x.11....2..x..4..x..9
..x..5..x.11..x....x..3..x..5..x....x..5..x..8..x....x..7..x.10..x
..8..x..9..x.12....8..x.10..x.12....6..x.10..x.12....5..x.11..x.12
		

Crossrefs

Column 5 of A215292.

Formula

a(n) = A060854(3,f3)*A060854(2,f4)*binomial(3*f3+2*f4,3*f3), where f3 = floor((n+1)/2) and f4 = floor(n/2).

A215291 Number of permutations of 0..floor((n*7-1)/2) on even squares of an nX7 array such that each row and column of even squares is increasing.

Original entry on oeis.org

1, 35, 2310, 210210, 42882840, 5703417720, 2061378118800, 337653735859440, 173457547735792320, 32436561426593163840, 21174123919831066023840, 4340695403565368534887200, 3373030378241974592216989200
Offset: 1

Views

Author

R. H. Hardin Aug 07 2012

Keywords

Comments

Column 7 of A215292

Examples

			Some solutions for n=3
..0..x..3..x..5..x..6....0..x..1..x..2..x..3....1..x..2..x..3..x..5
..x..1..x..8..x.10..x....x..5..x..8..x.10..x....x..0..x..6..x.10..x
..2..x..4..x..7..x..9....4..x..6..x..7..x..9....4..x..7..x..8..x..9
		

Formula

f3=floor((n+1)/2)
f4=floor(n/2)
a(n) = A060854(4,f3)*A060854(3,f4)*binomial(4*f3+3*f4,4*f3)
Showing 1-7 of 7 results.