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.

User: Alejandro H. Morales

Alejandro H. Morales's wiki page.

Alejandro H. Morales has authored 14 sequences. Here are the ten most recent ones:

A357593 Number of faces of the Minkowski sum of n simplices with vertices e_(i+1), e_(i+2), e_(i+3) for i=0,...,n-1, where e_i is a standard basis vector.

Original entry on oeis.org

8, 26, 88, 298, 1016, 3466, 11832, 40394, 137912, 470858
Offset: 1

Author

Alejandro H. Morales, Oct 05 2022

Keywords

Examples

			For n=1, the polytope is the simplex with vertices (1,0,0), (0,1,0), and (0,0,1) that has a(1)=8 faces (1 empty face, 3 vertices, 3 edges, and 1 facet).
		

Crossrefs

Programs

  • Sage
    def a(n): return add(PP(n,3,1).f_vector())
    def Delta(I,n):
        IM = identity_matrix(n)
        return Polyhedron(vertices=[IM[e] for e in I],backend='normaliz')
    def Py(n,SL,yL):
        return sum(yL[i]*Delta(SL[i],n) for i in range(len(SL)))
    def PP(n,k,s):
        SS = [set(range(s*i,k+s*i)) for i in range(n)],[1,]*(n)
        return Py(s*(n-1)+k,SS[0],SS[1])
    [a(n) for n in range(1,4)]

A357592 Number of edges of the Minkowski sum of n simplices with vertices e_(i+1), e_(i+2), e_(i+3) for i=0,...,n-1, where e_i is a standard basis vector.

Original entry on oeis.org

3, 11, 34, 96, 260, 683, 1757, 4447, 11114, 27493
Offset: 1

Author

Alejandro H. Morales, Oct 05 2022

Keywords

Crossrefs

Programs

  • Sage
    def a(n): return len(PP(n,3,1).graph().edges())
    def Delta(I,n):
        IM = identity_matrix(n)
        return Polyhedron(vertices=[IM[e] for e in I],backend='normaliz')
    def Py(n,SL,yL):
        return sum(yL[i]*Delta(SL[i],n) for i in range(len(SL)))
    def PP(n,k,s):
        SS = [set(range(s*i,k+s*i)) for i in range(n)],[1,]*(n)
        return Py(s*(n-1)+k,SS[0],SS[1])
    [a(n) for n in range(1,4)]

A357484 Number of linearity regions of a max-pooling function with a 3 by n input and 2 by 2 pooling windows.

Original entry on oeis.org

1, 14, 150, 1536, 15594, 158050, 1601356, 16223814, 164366170, 1665216896, 16870539234, 170917714410, 1731590444316, 17542976546494, 177730263461890, 1800609290091936, 18242215773029194, 184814350419581330, 1872379131238643436, 18969325721395559574
Offset: 1

Author

Alejandro H. Morales, Sep 30 2022

Keywords

Comments

a(n) is also the number of vertices of the Minkowski sum of 2*n-2 simplices conv(e_{i,j},e_{i,j+1},e_{i+1,j},e_{i+1,j+1}) for i=0,1 and j=0,...,n-2, viewing R^(3n) having basis {e_{i,j} | i=0,1,2; j=0,...,n-1}.

Examples

			For n = 2 the a(2)=14 vertices are (00,10), (00,11), (00,20), (00,21), (01,10), (01,11), (01,20), (01,21), (10,10), (10, 20), (10,21), (11,11), (11, 20), (11, 21), where (ij,kl) represents e_{i,j}+e_{k,l}. The pair (10,11) does not represent vertices since e_{1,0}+e_{1,1} is a convex combination of the vectors 2e_{1,0} + 2e_{1,1}. Ditto for the pair (11,10).
		

Crossrefs

Programs

  • Maple
    a:= proc(n) option remember;
       if n = 1 then
         return(1);
       elif n = 2 then
         return(14);
       elif n = 3 then
         return(150);
       elif n = 4 then
         return(1536);
       else
         return(13*a(n-1) - 31*a(n-2) + 20*a(n-3) - 4*a(n-4));
       end if;
    end proc:
    seq(a(n), n=1..20);
  • Mathematica
    LinearRecurrence[{13, -31, 20, -4}, {1, 14, 150, 1536}, 20] (* Hugo Pfoertner, Oct 05 2022 *)
  • Sage
    @cached_function
    def a(n):
        if n < 5: return [1, 14, 150, 1536][n - 1]
        return 13*a(n-1) - 31*a(n-2) + 20*a(n-3) - 4*a(n-4)
    print([a(n) for n in range(1, 21)])

Formula

a(n) = 13*a(n-1) - 31*a(n-2) + 20*a(n-3) - 4*a(n-4) for n>= 5.
G.f.: (x+x^2-x^3)/(1-13*x+31*x^2-20*x^3+4*x^4).

A347930 3-Springer numbers.

Original entry on oeis.org

1, 1, 3, 16, 88, 625, 5527, 55760, 640540, 8329326, 120212331, 1905939913, 32987637967, 618591571085, 12489644875037, 270193806214360, 6235154917414954, 152875655211527878, 3968729594485785289, 108754865309750398187, 3137052120203959610759
Offset: 2

Author

Alejandro H. Morales, Sep 19 2021

Keywords

Comments

a(n) is also the volume of a certain flow polytope.

Crossrefs

Programs

  • Maple
    wcomps:=proc(n,k)
           option remember;
    local ocomps,ncomps,i;
    ocomps:=combinat:-composition(n+k,k);
    ncomps:={};
    for i from 1 to nops(ocomps) do
       ncomps:=ncomps union{[seq(ocomps[i][j]-1,j=1..k)]};
    end do;
    return [op(ncomps)];
    end proc:
    b:=proc(s) option remember;
       local k;
       k := nops(s);
       if s = [seq(0,i=1..k)] then
          return(1);
       elif s[1]>0 then
          return(add(b([s[2]+j,op(s[3..k]),s[1]-j-1]),j=0..s[1]-1));
       else
          return(0);
       end if;
    end proc:a:=proc(n)   local N,S:   N := n-2;   S := wcomps(N,3);   return add(combinat:-multinomial(N,op(s))*b(s), s in S);end proc:seq(a(n),n=2..10);

Formula

a(n) = Sum_{(x,y,z), x+y+z=n-2} ((n-2)!/(x!*y!*z!))*b(x,y,z), where b(x,y,z) are the 3-Entringer numbers defined by Ramassamy.

A336674 Number of positive terms of the Okounkov-Olshanski formula for the number of standard tableaux of skew shape (n+3,n+2,...,1)/(n-1,n-2,...,1).

Original entry on oeis.org

1, 1, 5, 65, 1757, 87129, 7286709, 965911665, 193387756045, 56251615627273, 23021497112124901, 12903943243053179681, 9680994096074346690365, 9530338509606467082850745, 12099590059386455266220499477
Offset: 0

Author

Alejandro H. Morales, Jul 29 2020

Keywords

Comments

a(n) is also the number of semistandard Young tableaux of skew shape (n+3,n+2,...,1)/(n-1,n-2,...,1) such that the entries in row i are at most i for i=1,...,n+3.
a(n) is also the number of semistandard Young tableaux T of shape (n-1,n-2,...,1) such that j-i < T(i,j) <= n+3 for all cells (i,j).

Examples

			For n=2 the a(2)=5 semistandard Young tableaux of skew shape (5,4,3,2,1)/(1) are determined by their first column which are [1,2,3,4], [1,2,3,5], [1,2,4,5], [1,3,4,5], and [2,3,4,5]. Also, the a(2)=5 semistandard Young tableaux of shape (1) with entries between 0 and 5 are [1], [2], [3], [4], and [5]. Also, the a(3)=70-5=65 are the semistandard Young tableaux of shape (2,1) with entries at most 6 excluding the five tableaux whose entry in the first row and first column is 1: [[1,1],[2]], [[1,1],[3]], [[1,1],[4]], and [[1,1],[5]].
		

Crossrefs

A110501, A005700 gives the number of terms of the Naruse hook length formula for the same skew shape.

Programs

  • Maple
    b := proc(n)
        return 2*(-1)^n*(1-4^n)*bernoulli(2*n)/factorial(2*n);
    end proc:
    a := proc(n)
        return factorial(2*n+4)*factorial(2*n+6)*(b(n+1)*b(n+3)-b(n+2)^2)/6;
    end proc:
    seq(a(n),n=0..10);
  • Sage
    def b(n):
        return 2*(-1)^n*(1-4^n)*bernoulli(2*n)/factorial(2*n) ;
    def a(n):
        return factorial(2*n+4)*factorial(2*n+6)*(b(n+1)*b(n+3)-b(n+2)^2)/6;
    [a(i) for i in range(10)]

Formula

a(n) = ((2*n+4)!*(2*n+6)!/3!)*(b(n+1)*b(n+3)-b(n+2)^2) where b(n)=A110501(n)/(2*n)!.

A331799 Normalized volume of the Caracol flow polytope. Also equal to the number of "unified diagrams" of the Caracol graph (see Section 4.3 and Section 5 in Benedetti et al. reference).

Original entry on oeis.org

1, 3, 32, 625, 18144, 705894, 34603008, 2051893701, 143000000000, 11464341673642, 1039964049506304, 105353940923859082, 11793014101010071552, 1445828316284179687500, 192713711798795989155840, 27750747808814680091687085, 4293818865468117678192721920
Offset: 1

Author

Alejandro H. Morales, Jan 26 2020

Keywords

Examples

			For n=3, a(3) = 32 = 2*(3+1)^2.
		

Crossrefs

Programs

  • Maple
    a:=proc(n)
      return (1/n)*binomial(2*n-2,n-1)*(n+1)^(n-1);
    end proc:
  • Mathematica
    Array[(1/#) Binomial[2 # - 2, # - 1] (# + 1)^(# - 1) &, 17] (* Michael De Vlieger, Jan 28 2020 *)

Formula

a(n) = A000108(n-1)*A000272(n+1).
a(n) = (1/n)*binomial(2*n-2,n-1)*(n+1)^(n-1).
a(n) = Sum_{i>=0..n-1} binomial(2*n-2,i)*A329057(n-1,i).

A291908 Number of standard Young tableaux of skew shape lambda/mu where lambda is the staircase (4*n-1,4*n-2,...,2,1) and mu is the square n^n.

Original entry on oeis.org

1, 16, 4362327818240, 19265181532031090042534736325278852710400, 830325323503973129435791248069702287019820905338483131168940909920954227594481411031040
Offset: 0

Author

Alejandro H. Morales, Sep 05 2017

Keywords

Comments

The number of standard Young tableaux of a fixed skew shape has a determinantal formula, the Jacobi-Trudi formula. It is rare when a family of skew shapes has a product formula for the number of standard Young tableaux. This product formula has independently been proved using P-Schur functions (by DeWitt) and using the Naruse hook-length formula for skew shapes (by Morales, Pak and Panova).

Examples

			a(1)=16 since there are 16 standard Young tableaux of skew shape 321/1 since this is the same as the number of standard Young tableaux of straight shape 321 given by the hook-length formula: 16 = 6!/(3^2*5).
		

Programs

  • Maple
    b:=n->mul(factorial(i),i=1..n-1):
    c:=n->mul(doublefactorial(2*i-1),i=1..n-1):
    a:=n->factorial(binomial(4*n,2)-n^2)*b(n)^3*b(3*n)*c(n)*c(3*n)/(b(2*n)^3*c(2*n)^2*c(4*n)):
    seq(a(n),n=0..9);
  • Sage
    def b(n): return mul([factorial(i) for i in range(1,n)])
    def d(n): return factorial(n+1)/(2^((n+1)/2)*factorial((n+1)/2))
    def c(n): return mul([d(2*i-1) for i in range(1,n)])
    def a(n):
        return factorial(binomial(4*n,2)-n^2)*b(n)^3*b(3*n)*c(n)*c(3*n)/(b(2*n)^3*c(2*n)^2*c(4*n))
    [a(n) for n in range(10)]

Formula

a(n) = (binomial(4*n,2)-n^2)!*b(n)^3*b(3*n)*c(n)*c(3*n)/(b(2*n)^3*c(2*n)^2*c(4*n)) where b(n) = 1!*2!*...*(n-1)! is the superfactorial A000178(n-1), and c(n) = 1!!*3!!*...*(2*n-3)!! is super doublefactorial A057863(n-1).
a(n) ~ sqrt(Pi) * 3^(9*n^2 - 3*n/2 - 1/24) * 7^(7*n^2 - 2*n + 1/2) * exp(7*n^2/2 - 2*n + 23/56) * n^(7*n^2 - 2*n + 7/8) / (A^(3/2) * 2^(33*n^2 - 6*n - 7/8)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Apr 08 2021

A291879 Number of monomials of the Schubert polynomial of the permutation 351624 tensor 1^n.

Original entry on oeis.org

1, 8, 6720, 561120560, 4557185891241984, 3571558033324129373292768, 269111599998006391761541640176800000, 1945556482213500279178010210766074095827609600000, 1347912754604769492992184400055703948513202427323999206349209600
Offset: 0

Author

Alejandro H. Morales, Sep 05 2017

Keywords

Comments

The permutation 351624 tensor 1^n is the permutation whose permutation matrix is obtained from that of 351624 by replacing each 1 with an n X n identity matrix.

Examples

			For n=1 we have that a(1)=8 since the Schubert polynomial of 351624 equals the following sum of eight monomials: x0^3*x1^3*x2 + x0^3*x1^2*x2^2 + x0^2*x1^3*x2^2 + x0^3*x1^3*x3 + x0^3*x1^2*x2*x3 + x0^2*x1^3*x2*x3 + x0^3*x1^2*x3^2 + x0^2*x1^3*x3^2.
		

Crossrefs

Programs

  • Mathematica
    Table[BarnesG[n + 1]^5 * BarnesG[3*n + 1]^2 * BarnesG[5*n + 1] / (BarnesG[2*n + 1]^4 * BarnesG[4*n + 1]^2), {n, 0, 10}] (* Vaclav Kotesovec, Apr 08 2021 *)
  • PARI
    b(n) = prod(k=1, n-1, k!);
    a(n) = b(n)^5*b(3*n)^2*b(5*n)/(b(2*n)^4*b(4*n)^2); \\ Michel Marcus, Sep 07 2017
  • Sage
    def b(n): return mul([factorial(i) for i in range(1,n)])
    def a(n): return b(n)^5*b(3*n)^2*b(5*n)/(b(2*n)^4*b(4*n)^2)
    [a(n) for n in range(10)]
    

Formula

a(n) = b(n)^5*b(3*n)^2*b(5*n)/(b(2*n)^4*b(4*n)^2) where b(n) = 1!*2!*...*(n-1)! is a superfactorial A000178(n-1). [corrected by Vaclav Kotesovec, Apr 08 2021]
a(n) = c(n)*b(3*n)^2*b(6*n)/((7*n^2)!*b(2*n)^2*b(4*n)^2) where b(n) = 1!*2!*...*(n-1)! is a superfactorial A000178(n-1) and c(n) = A291871.
a(n) ~ exp(1/6) * 3^(9*n^2 - 1/6) * 5^(25*n^2/2 - 1/12) / (A^2 * n^(1/6) * 2^(40*n^2 - 2/3)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Apr 08 2021

A291871 Number of standard Young tableaux of skew shape (3*n^(2*n), 2*n^n)/(n^n).

Original entry on oeis.org

1, 42, 14617044842400, 5458228515594914179387748450655273588000, 864891828322912925373153355728411014930091519471102108791040960580578545212124160000
Offset: 0

Author

Alejandro H. Morales, Sep 04 2017

Keywords

Comments

The number of standard Young tableaux of a fixed skew shape has a determinantal formula, the Jacobi-Trudi formula. It is rare when a family of skew shapes has a product formula for the number of standard Young tableaux. This product formula has independently been proved using a combinatorial model for the Selberg integral (by Kim and Oh) and using the Naruse hook-length formula for skew shapes (by Morales, Pak and Panova).

Examples

			a(1)=42 since there are 42 standard Young tableaux of skew shape 332/1 since this is the same as the number of standard Young tableaux of straight shape 332 given by the hook-length formula: 42 = 8!/(2^2*3*4^2*5).
		

Programs

  • Maple
    b:=n->mul(factorial(i),i=1..n-1):
    a:=n->factorial(7*n^2)*b(n)^5*b(5*n)/(b(2*n)^2*b(6*n)):
    seq(a(i),i=0..9);
  • Mathematica
    b[n_] := Product[i!, {i, n - 1}]; Table[(7 n^2)!*b[n]^5*b[5 n]/(b[2 n]^2*b[6 n]), {n, 0, 4}] (* Michael De Vlieger, Sep 10 2017 *)
  • Sage
    def b(n): return mul([factorial(i) for i in range(1,n)])
    def a(n): return factorial(7*n^2)*b(n)^5*b(5*n)/(b(2*n)^2*b(6*n))
    [a(n) for n in range(10)]

Formula

a(n) = (7*n^2)!*b(n)^5*b(5*n)/(b(2*n)^2*b(6*n)) where b(n) = 1!*2!*...*(n-1)! is a superfactorial A000178(n-1).
a(n) = (7*n^2)!*c(n)*b(n)^2*b(2*n)*b(5*n)/(b(6*n)*b(3*n)) where b(n) = 1!*2!*...*(n-1)! is a superfactorial A000178(n-1) and c(n) = A008793.
log a(n) = 7*n^2*log(n) + (75/2 - 15*log(2) - 18*log(3) + 25/2*log(5) + 7*log(7))*n^2 + O(n*log(n)). (See Example 6.2 in Morales et al.)
a(n) ~ sqrt(Pi) * 5^(25*n^2/2 - 1/12) * 7^(7*n^2 + 1/2) * exp(7*n^2/2 + 1/4) * n^(7*n^2 + 3/4) / (A^3 * 2^(22*n^2 - 3/4) * 3^(18*n^2 - 1/12)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Apr 08 2021

A278289 Number of standard Young tableaux of skew shape (2n-1,2n-2,...,2,1)/(n-1,n-2,..,2,1).

Original entry on oeis.org

1, 1, 16, 101376, 1190156828672, 68978321274090930831360, 40824193474825703180733027309531955200, 440873872874088459550341319780612789503586208384381091840, 140992383930585613207663170866505518985873138480180692888967131590224605582721024
Offset: 0

Author

Alejandro H. Morales, Nov 16 2016

Keywords

Examples

			For n = 3 there are a(2) = 16 standard tableaux of shape (3,2,1)/(1).
		

References

  • R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Corollary 7.16.3.

Crossrefs

Cf. A005118; for even n the number of terms in Naruse hook length formula is given by A181119 (Corollary 8.1 in arXiv:1610.04744).

Programs

  • Maple
    a:=proc(k) local lam,mu;
    lam:=[seq(2*k-i,i=1..2*k-1)];
    mu:=[seq(k-i,i=1..k-1),seq(0,i=1..k)];
    factorial(binomial(2*k,2)-binomial(k,2))*LinearAlgebra:-Determinant(Matrix(2*k-1, 2*k-1,(i,j)->`if`(lam[i]-mu[j]-i+j<0,0,1/factorial(lam[i]-mu[j]-i+j))));
    end proc:
    seq(a(n),n=0..5);

Formula

a(n) = ((3*n^2-n)/2)!*det(1/(lambda[i]-mu[j]-i+j)!), where lambda = (2*n-1,2*n-2,...,1) and mu = (n-1,n-2,...,1,0...,0).
There is a constant c such that log(a(k)) = n*log(n)/2 + c*n + o(n) where n = k*(3*k-1)/2 goes to infinity and -0.2368 <= c <= -0.1648. [updated by Alejandro H. Morales, Aug 29 2020]