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.

Previous Showing 31-39 of 39 results.

A177848 Triangle, read by rows, T(n, k) = t(k, n-k+1) - t(1, n) + 1 where t(n, m) = (n*m)!*Beta(n, m).

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 55, 55, 1, 1, 1993, 12073, 1993, 1, 1, 120841, 7983241, 7983241, 120841, 1, 1, 11404081, 12454040881, 149448498481, 12454040881, 11404081, 1, 1, 1556750161, 38109367290961, 8688935743482961, 8688935743482961, 38109367290961, 1556750161, 1
Offset: 1

Views

Author

Roger L. Bagula, May 14 2010

Keywords

Comments

Row sums are {1, 2, 5, 112, 16061, 16208166, 174379388407, 17454093335048168, 27083470639271574245769, 421762213493139881153379087370, ...}.

Examples

			Triangle begins as:
  1;
  1,        1;
  1,        3,           1;
  1,       55,          55,            1;
  1,     1993,       12073,         1993,           1;
  1,   120841,     7983241,      7983241,      120841,        1;
  1, 11404081, 12454040881, 149448498481, 12454040881, 11404081, 1;
		

Crossrefs

Cf. A060854.

Programs

  • Mathematica
    t[n_, k_]:= (n*k)!*Beta[n, k];
    Table[t[k, n-k+1] - t[1, n] + 1, {n, 12}, {k, n}]//Flatten
  • Sage
    def t(n, k): return factorial(n*k)*beta(n, k)
    flatten([[t(k, n-k+1) - t(1,n) + 1 for k in (1..n)] for n in (1..12)]) # G. C. Greubel, Feb 06 2021

Formula

Let t(n, k) = (n*k)!*Beta(n, k) then T(n, k) = t(k, n-k+1) - t(1, n) + 1.

Extensions

Edited by G. C. Greubel, Feb 06 2021

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)

A215293 Number of permutations of 0..floor((n*n-2)/2) on odd squares of an n X n array such that each row and column of odd squares is increasing.

Original entry on oeis.org

1, 2, 6, 280, 23100, 85765680, 577185873264, 346915095471584640, 381134230556959188429120, 62144711688730139887005809020800, 18592619468814454675301397184588597886400, 1236552808693429892089668394551052130596983991526400, 151213938214745201135492692441902799026853717717324113365952000
Offset: 1

Views

Author

R. H. Hardin, Aug 07 2012

Keywords

Examples

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

Crossrefs

Diagonal of A215297.
Cf. A060854.

Formula

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

A215294 Number of permutations of 0..floor((n*3-2)/2) on odd squares of an n X 3 array such that each row and column of odd squares is increasing.

Original entry on oeis.org

1, 3, 6, 30, 70, 420, 1050, 6930, 18018, 126126, 336336, 2450448, 6651216, 49884120, 137181330, 1051723530, 2921454250, 22787343150, 63804560820, 504636071940, 1422156202740, 11377249621920, 32235540595440, 260363981732400
Offset: 1

Views

Author

R. H. Hardin, Aug 07 2012

Keywords

Comments

a(n) is number of symmetric standard Young tableaux of shape (n,n,n). - Ran Pan, May 21 2015

Examples

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

Crossrefs

Column 3 of A215297.
Cf. A060693.

Programs

  • Maple
    a := n -> `if`(irem(n, 2) = 0, ((1/2)*n+1)*factorial((3/2)*n)/ (factorial((1/2)*n+1)^2*factorial((1/2)*n)), factorial((3/2)*n+3/2)/ (factorial((1/2)*n+1/2)^3*((9/2)*n+3/2))): # Peter Luschny, Sep 30 2018

Formula

a(n) = A060854(1,f3)*A060854(2,f4)*binomial(1*f3+2*f4,1*f3) where f3 = floor((n+1)/2), f4 = floor(n/2).
a(n) = e(n) if n even otherwise o(n), where e(n) = 6*Gamma((3*n)/2)/((2 + n)*Gamma(1 + n/2)^2*Gamma(n/2)) and o(n) = (1 + n)*Gamma(1/2 + (3*n)/2)/(2*Gamma((3 + n)/2)^3). - Peter Luschny, Sep 30 2018

A215295 Number of permutations of 0..floor((n*5-2)/2) on odd squares of an nX5 array such that each row and column of odd squares is increasing.

Original entry on oeis.org

1, 10, 70, 2100, 23100, 1051050, 14294280, 814773960, 12547518984, 824551247520, 13781785137120, 999179422441200, 17699749768958400, 1379105502831342000, 25513451802379827000, 2100607531729272423000, 40191624107086745693400
Offset: 1

Views

Author

R. H. Hardin Aug 07 2012

Keywords

Comments

Column 5 of A215297

Examples

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

Formula

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

A215296 Number of permutations of 0..floor((n*7-2)/2) on odd squares of an nX7 array such that each row and column of odd squares is increasing.

Original entry on oeis.org

1, 35, 1050, 210210, 14294280, 5703417720, 577185873264, 337653735859440, 43364386933948080, 32436561426593163840, 4886336289191784467040, 4340695403565368534887200, 733267473530864041786302000
Offset: 1

Views

Author

R. H. Hardin Aug 07 2012

Keywords

Comments

Column 7 of A215297

Examples

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

Formula

f3=floor((n+1)/2)
f4=floor(n/2)
a(n) = A060854(3,f3)*A060854(4,f4)*binomial(3*f3+4*f4,3*f3)

A378173 Array read by antidiagonals: T(n,k) is the number of proper antichain partitions of the rectangular poset of size n X k.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 5, 5, 1, 1, 14, 38, 14, 1, 1, 42, 372, 372, 42, 1, 1, 132, 4282, 14606, 4282, 132, 1, 1, 429, 55149
Offset: 1

Views

Author

Ludovic Schwob, Nov 18 2024

Keywords

Comments

A partition of a poset into antichains is said to be proper if it does not contain two antichains A_1 and A_2, with x_1,y_1 in A_1 and x_2,y_2 in A_2, such that x_1y_2.
A proper antichain partition of a poset is endowed with an order relation, which is induced by the order relation of the poset. Let Y be a young diagram, and P the poset of shape Y. The number of linear extensions of P is the number of standard Young tableaux with shape Y. The sum over all proper antichain partitions of P, of the numbers of linear extensions of the induced orders, is equal to the number of normal generalized Young tableaux of shape Y with all rows and columns strictly increasing (cf. A299968).

Examples

			Array begins:
=====================================================================
n/k | 1     2      3      4      5      6 ...
----+----------------------------------------------------------------
  1 | 1     1      1      1      1      1 ...
  2 | 1     2      5     14     42    132 ...
  3 | 1     5     38    372   4282  55149 ...
  4 | 1    14    372  14606 ...
  5 | 1    42   4282 ...
  6 | 1   132  55149 ...
		

Crossrefs

Formula

T(n,k) = T(k,n).
T(n,2) = A000108(n).
Previous Showing 31-39 of 39 results.