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.

A008793 The problem of the calissons: number of ways to tile a hexagon of edge n with diamonds of side 1. Also number of plane partitions whose Young diagrams fit inside an n X n X n box.

Original entry on oeis.org

1, 2, 20, 980, 232848, 267227532, 1478619421136, 39405996318420160, 5055160684040254910720, 3120344782196754906063540800, 9265037718181937012241727284450000, 132307448895406086706107959899799334375000
Offset: 0

Views

Author

Keywords

Comments

The 3-dimensional analog of A000984. - William Entriken, Aug 06 2013
The largest prime factor of a(n) is the largest prime p < 3*n. Its multiplicity is equal to 3*n-p. This can be proved with the formula of Michel Marcus, for example. - Walter Trump, Feb 11 2023
a(n) is also the number of resonance structures of circumcircum...coronene, where circum is repeated n-2 times where a(1) is the number of resonance structures of benzene (see Gutman et al.). - Yuan Yao, Oct 29 2023

References

  • Miklos Bona, editor, Handbook of Enumerative Combinatorics, CRC Press, 2015, page 545, also p. 575 line -1 with a=b=c=n.
  • D. M. Bressoud, Proofs and Confirmations, Camb. Univ. Press, 1999; Eq. (6.8), p. 198. The first printing of Eq. (6.8) is wrong (see A049505 and A005157), but if one changes the limits in the formula (before it is corrected) to {1 <= i <= r, 1 <= j <= r}, one obtains the present sequence. - N. J. A. Sloane, Jun 30 2013
  • Gordon G. Cash and Jerry Ray Dias, Computation, Properties and Resonance Topology of Benzenoid Monoradicals and Polyradicals and the Eigenvectors Belonging to Their Zero Eigenvalues, J. Math. Chem., 30 (2001), 429-444. [See K, p. 442.]
  • Sebastien Desreux, Martin Matamala, Ivan Rapaport, Eric Remila, Domino tilings and related models: space of configurations of domains with holes, arXiv:math/0302344, 27 Feb 2003
  • Anne S. Meeussen, Erdal C. Oguz, Yair Shokef, Martin van Hecke1, Topological defects produce exotic mechanics in complex metamaterials, arXiv preprint 1903.07919, 2019 [See Section "Compatible metamaterials with fully antiferromagnetic interactions" - N. J. A. Sloane, Mar 23 2019]
  • J. Propp, Enumeration of matchings: problems and progress, pp. 255-291 in L. J. Billera et al., eds, New Perspectives in Algebraic Combinatorics, Cambridge, 1999 (see p. 261).

Crossrefs

Cf. A000984, A066931, A352656, A352657. Main diagonal of array A103905.

Programs

  • Maple
    A008793 := proc(n) local i; mul((i - 1)!*(i + 2*n - 1)!/((i + n - 1)!)^2, i = 1 .. n) end proc;
  • Mathematica
    Table[ Product[ (i+j+k-1)/(i+j+k-2), {i, n}, {j, n}, {k, n} ], {n, 10} ]
  • PARI
    a(n) = prod(i=1,n, prod(j=1, n, (n+i+j-1)/(i+j-1))); \\ Michel Marcus, Jul 13 2020

Formula

a(n) = Product_{i = 0..n-1} (i^(-i)*(n+i)^(2*i-n)*(2*n+i)^(n-i)).
a(n) = Product_{i = 1..n} Product_{j = 0..n-1} (3*n-i-j)/(2*n-i-j).
a(n) = Product_{i = 1..n} Gamma[i]*Gamma[i+2*n]/Gamma[i+n]^2.
a(n) = Product_{i = 0..n-1} i!*(i+2*n)!/(i+n)!^2.
a(n) = Product_{i = 1..n} Product_{j = n..2*n-1} i+j / Product_{j = 0..n-1} i+j. - Paul Barry, Jun 13 2006
For n >= 1, a(n) = det(binomial(2*n,n+i-j)) for 1<=i,j<=n [Krattenhaller, Theorem 4, with a = b = c = n].
Let H(n) = Product_{k = 1..n-1} k!. Then for a,b,c nonnegative integers (H(a)*H(b)*H(c)*H(a+b+c))/(H(a+b)*H(b+c)*H(c+a)) is an integer [MacMahon, Chapter II, Section 429, p. 182, with x -> 1]. Setting a = b = c = n gives the entries for this sequence. - Peter Bala, Dec 22 2011
a(n) ~ exp(1/12) * 3^(9*n^2/2 - 1/12) / (A * n^(1/12) * 2^(6*n^2 - 1/4)), where A = A074962 = 1.28242712910062263687534256886979... is the Glaisher-Kinkelin constant. - Vaclav Kotesovec, Feb 27 2015
a(n) = Product_{i = 1..n} Product_{j = 1..n} (n+i+j-1)/(i+j-1). - Michel Marcus, Jul 13 2020
Conjecture: the supercongruences a(n*p^r) == a(n*p^(r-1))^p (mod p^(4*r)) hold for all primes p and positive integers n and r. - Peter Bala, Apr 07 2022

Extensions

More terms from Eric W. Weisstein

A049505 a(n) = Product_{1<=i<=j<=n} (i+j+n-1)/(i+j-1), number of symmetric plane partitions in n-cube.

Original entry on oeis.org

1, 2, 10, 112, 2772, 151008, 18076916, 4751252480, 2740612658576, 3468301123758080, 9627912669442441500, 58618653300361405440000, 782683432110638830001250000, 22916694891747599820616089600000, 1471328419282772010324439370939640000
Offset: 0

Views

Author

Keywords

Comments

The first printing of the Bressoud book states that the formula Product_{1<=i<=j<=n} (i+j+n-1)/(i+j-1) in Eq. (6.8) is the number of totally symmetric plane partitions. This is wrong, although it does produce the current sequence. For the correct formula for the number of totally symmetric plane partitions see A005157.

References

  • D. M. Bressoud, Proofs and Confirmations, Camb. Univ. Press, 1999; Eq. (6.8), p. 198.

Crossrefs

Main diagonal of array A102539.
Main diagonal of array in A073165.

Programs

  • Maple
    A049505 := proc(n) local i,j; mul(mul((i+j+n-1)/(i+j-1),j=i..n),i=1..n); end;
  • Mathematica
    a[n_] := Product[ ((2i-2)!*(i+2n-1)!)/((i+n-1)!*(2i+n-2)!), {i, 1, n}]; Table[a[n], {n, 0, 14}] (* Jean-François Alcover, Jun 22 2012, after PARI *)
  • PARI
    a(n)=prod(i=1,n,prod(j=i,n,(i+j+n-1)/(i+j-1)))

Formula

a(n) = Product_{1<=i<=j<=n} (i+j+n-1)/(i+j-1).
a(n) = Product_{i=1..n} (((2*i-2)!*(i+2*n-1)!)/((i+n-1)!*(2*i+n-2)!)). - Jean-François Alcover, Jun 22 2012
a(n) = Product_{i=1..n} (binomial((i-1) + 2*n, n)/binomial(n + 2*(i-1), n)). - Olivier Gérard, Feb 25 2015
a(n) ~ exp(1/24) * 3^(9*n^2/4 + 3*n/4 - 1/24) / (A^(1/2) * n^(1/24) * 2^(3*n^2 + n/2 + 1/8)), where A = A074962 = 1.2824271291... is the Glaisher-Kinkelin constant. - Vaclav Kotesovec, Mar 01 2015
From Peter Bala, Feb 15 2023: (Start)
a(n+1) = m(n)*a(n) where m(n) = ((3*n + 2)!*n!^2)/((2 n)!*(2 n + 1)!^2) * Product_{i = 1..n} n + 2*i for n >= 1.
Conjectures:
1) the supercongruence a(p) == 2^((p+1)/2) (mod p^3) holds for all primes p >= 3 (checked up to p = 1009).
2) the congruence a(p^2) == (-1)^((p^2-1)/8)*a(p)^(p^2-p+1) (mod p^3) holds for all primes p >= 3 (checked up to p = 89).
3) the congruence a(p^3) == a(p^2)^((p^3-p^2+2)/2) (mod p^3) holds for all primes p >= 2. (End)

Extensions

Edited by N. J. A. Sloane, Jun 30 2013; codes and formula checked by N. J. A. Sloane and Olivier Gérard

A184173 Triangle read by rows: T(n,k) is the sum of the k X k minors in the n X n Pascal matrix (0<=k<=n; the empty 0 X 0 minor is defined to be 1).

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 7, 7, 1, 1, 15, 34, 15, 1, 1, 31, 144, 144, 31, 1, 1, 63, 574, 1155, 574, 63, 1, 1, 127, 2226, 8526, 8526, 2226, 127, 1, 1, 255, 8533, 60588, 113832, 60588, 8533, 255, 1, 1, 511, 32587, 424117, 1444608, 1444608, 424117, 32587, 511, 1
Offset: 0

Views

Author

Emeric Deutsch, Jan 12 2011

Keywords

Comments

Apparently, the sum of the entries in row n is A005157(n).

Examples

			T(3,1) = 7 because in the 3 X 3 Pascal matrix [1,0,0/1,1,0/1,2,1] the sum of the entries is 7.
Triangle starts:
  1;
  1,   1;
  1,   3,    1;
  1,   7,    7,    1;
  1,  15,   34,   15,    1;
  1,  31,  144,  144,   31,    1;
  1,  63,  574, 1155,  574,   63,   1;
  1, 127, 2226, 8526, 8526, 2226, 127, 1;
  ...
		

Crossrefs

Columns k=0-2 give: A000012, A000225, A306376.

Programs

  • Maple
    with(combinat): with(LinearAlgebra):
    T:= proc(n, k) option remember; `if`(n-k add(add(
          Determinant(SubMatrix(Matrix(n, (i, j)-> binomial(i-1, j-1)),
           i, j)), j in l), i in l))(choose([$1..n], k)))
        end:
    seq(seq(T(n, k), k=0..n), n=0..7);  # Alois P. Heinz, Feb 11 2019
  • Mathematica
    T[n_, k_] := T[n, k] = If[k == 0 || k == n, 1, Module[{l, M},
        l = Subsets[Range[n], {k}];
        M = Table[Binomial[i-1, j-1], {i, n}, {j, n}];
        Total[Det /@ Flatten[Table[M[[i, j]], {i, l}, {j, l}], 1]]]];
    Table[T[n, k], {n, 0, 9}, {k, 0, n}] // Flatten (* Jean-François Alcover, Dec 09 2019 updated Feb 29 2024 *)

Formula

The triangle is symmetric: T(n,k) = T(n,n-k).

Extensions

Typo corrected by Alois P. Heinz, Feb 11 2019

A323848 Irregular triangle read by rows: T(n,d) (n >= 1, d <= n-1 for n>1) = number of n X n integer-valued matrices M such that M_{1,1}=0, M_{n,n}=d, M_{(i+1),j} = M_{i,j} + (0 or 1), M_{i,(j+1)} = M_{i,j} + (0 or 1), and M_{(i+1),(j+1)} = M_{i,j} + (0 or 1).

Original entry on oeis.org

0, 4, 18, 25, 68, 386, 256, 250, 4657, 12200, 4356, 922, 54219, 432842, 608993, 123904, 3430, 642815, 14697256, 60650883, 49489706, 5909761, 12868, 7852836, 514608568, 5713126349, 13458882036, 6648891794, 473497600, 48618, 98755951, 18971384148, 558848240787, 3406380649146, 4857082197177, 1489334202216, 63799687396
Offset: 1

Views

Author

N. J. A. Sloane, Feb 07 2019

Keywords

Comments

T(n,n-1) = A005157(n-1)^2 for n >= 2. See Knuth (2019) link.

Examples

			Triangle begins:
  n\d    1      2        3        4        5       6  7
   1     0      0        0        0        0       0  0
   2     4      0        0        0        0       0  0
   3    18     25        0        0        0       0  0
   4    68    386      256        0        0       0  0
   5   250   4657    12200     4356        0       0  0
   6   922  54219   432842   608993   123904       0  0
   7  3430 642815 14697256 60650883 49489706 5909761  0
...
		

References

  • D. E. Knuth, Email to N. J. A. Sloane, Feb 06 2019.

Crossrefs

Columns d=1-2 give: A115112, A306322.

Formula

T(n,1) = binomial(2n,n) - 2.

Extensions

More terms from Alois P. Heinz, Feb 07 2019

A214564 Number T(n,k) of totally symmetric plane partitions with largest part <= n and exactly k orbits under action of the symmetric group S_3; triangle T(n,k), n>=0, 0<=k<=A000292(n), read by rows.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 3, 3, 4, 5, 5, 5, 6, 5, 5, 5, 4, 3, 3, 2, 1, 1, 1, 1, 1, 1, 2, 3, 4, 5, 7, 8, 10, 12, 13, 15, 17, 18, 19, 20, 20, 20, 20, 19, 18, 17, 15, 13, 12, 10, 8, 7, 5, 4, 3, 2, 1, 1, 1
Offset: 0

Views

Author

Alois P. Heinz, Jul 21 2012

Keywords

Examples

			Triangle T(n,k) begins:
  1;
  1, 1;
  1, 1, 1, 1, 1;
  1, 1, 1, 2, 2, 2, 2, 2, 1,  1,  1;
  1, 1, 1, 2, 3, 3, 4, 5, 5,  5,  6,  5,  5,  5,  4,  3,  3,  2,  1,  1,  1;
  1, 1, 1, 2, 3, 4, 5, 7, 8, 10, 12, 13, 15, 17, 18, 19, 20, 20, 20, 20, 19, ...
  ...
		

Crossrefs

Row sums give: A005157.
Cf. A000292.

Programs

  • Maple
    gf:= n-> simplify(mul(mul(mul( (1-q^(i+j+k-1))/
             (1-q^(i+j+k-2)), i=1..j), j=1..k), k=1..n)):
    T:= n-> seq(coeff(gf(n), q, k), k=0..n*(n+1)*(n+2)/6):
    seq(T(n), n=0..7);

Formula

G.f. of row n: Product_{1<=i<=j<=k<=n} (1-q^(i+j+k-1))/(1-q^(i+j+k-2)).

A266091 a(n) = Product_{k=0..n} (3*k)!/(n+k)!.

Original entry on oeis.org

1, 3, 15, 126, 1782, 42471, 1706562, 115640460, 13216815036, 2548124192970, 828751754742975, 454739496669274500, 420972227408592675000, 657522745057190417409000, 1732789066323343611643088400, 7704900186426840030325195822560, 57807195523790513335568376591463776
Offset: 0

Views

Author

Michel Marcus, Dec 21 2015

Keywords

Comments

a(n) gives the number of diagonally and antidiagonally symmetric alternating sign matrices (DASASM's) of order (2n+1) X (2n+1) (see Behrend et al. link).

Crossrefs

Programs

  • Magma
    [&*[Factorial(3*k)/Factorial(n+k): k in [0..n]]: n in [0..16]]; // Vincenzo Librandi, Dec 21 2015
  • Mathematica
    Table[Product[(3 k)!/(n + k)!, {k, 0, n}], {n, 0, 16}] (* Vincenzo Librandi, Dec 21 2015 *)
  • PARI
    a(n) = prod(k=0, n, (3*k)!/(n+k)!);
    

Formula

a(n) ~ Gamma(1/3)^(1/3) * exp(1/36) * n^(1/36) * 3^(3*n^2/2 + 2*n + 11/36) / (A^(1/3) * Pi^(1/6) * 2^(2*n^2 + 2*n + 7/12)), where A = A074962 is the Glaisher-Kinkelin constant. - Vaclav Kotesovec, Dec 21 2015
a(n) = Product_{1 <= i <= j <= n} (i + 2*j)/(i + j - 1). Note that Product_{1 <= i <= j <= n} (i + j)/(i + j - 1) = 2^n. - Peter Bala, Feb 19 2023

A236691 Number of totally symmetric solid partitions which fit in an n X n X n X n box.

Original entry on oeis.org

1, 2, 6, 32, 352, 9304, 683464, 161960220
Offset: 0

Views

Author

Graham H. Hawkes, Jan 30 2014

Keywords

Comments

Also, for n > 0, the number of totally symmetric (n-1)-dimensional partitions which fit in an (n-1)-dimensional box whose sides all have length 5.
There is no conjectured formula for a(n).
The formula a(n,d) = Product_{i_1=1..n} Product_{i_2=i_1..n} ... Product_{i_d=i_(d-1)..n} (i_1+i_2+...+i_d-d+2)/(i_1+i_2+...+i_d-d+1) gives the number of totally symmetric d-dimensional partitions that fit in a box whose sides all have length n, for d = 1, 2, and 3. For d > 3 this formula fails. In particular, when d=4 it produces the sequence: 1, 2, 6, 32, 352, 9216, 661504, ... rather than the sequence above.

Crossrefs

This is the 4-dimensional case. Dimensions 1, 2, and 3 are respectively given by A000027, A000079, and A005157.
Cf. A097516.
Showing 1-7 of 7 results.