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
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).
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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
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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
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).
- Laura Escobar, Patricio Gallardo, Javier González-Anaya, José L. González, Guido Montúfar, and Alejandro H. Morales, Enumeration of max-pooling responses with generalized permutohedra, arXiv:2209.14978 [math.CO], 2022.
- Index entries for linear recurrences with constant coefficients, signature (13,-31,20,-4).
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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);
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LinearRecurrence[{13, -31, 20, -4}, {1, 14, 150, 1536}, 20] (* Hugo Pfoertner, Oct 05 2022 *)
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@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)])
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
- Arvind Ayyer, Matthieu Josuat-Vergès, and Sanjay Ramassamy, Extensions of partial cyclic orders and consecutive coordinate polytopes, Ann. H. Lebesgue, 3 (2020), 275-297.
- R. S. Gonzalez D'Leon, A. H. Morales, C. R. H. Hanusa, and M. Yip, Column convex matrices, G-cyclic orders, and flow polytopes, arXiv:2107.07326 [math.CO], 2021.
- S. Ramassamy, Extensions of partial cyclic orders, Euler numbers and multidimensional boustrophedons, Electron. J. Combin., 25 (2018), #P1.66.
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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);
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
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]].
A110501,
A005700 gives the number of terms of the Naruse hook length formula for the same skew shape.
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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);
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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)]
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
For n=3, a(3) = 32 = 2*(3+1)^2.
- C. Benedetti, R. S. González D'León, C. Hanusa, P. E. Harris, A. Khare, A. H. Morales, M. Yip, A combinatorial model for computing volumes of flow polytopes, arXiv:1801.07684 [math.CO], 2018-2019.
- C. Benedetti, R. S. González D'León, C. Hanusa, P. E. Harris, A. Khare, A. H. Morales, M. Yip, A combinatorial model for computing volumes of flow polytopes, Trans. Amer. Math. Soc., 372 (2019), 3369-3404.
- J. Jang and J. S. Kim, Volumes of flow polytopes related to caracol graphs, arXiv:1911.10703 [math.CO], 2019
- M. Yip, A Fuss-Catalan variation of the caracol flow polytope, arXiv:1910.10060 [math.CO], 2019.
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a:=proc(n)
return (1/n)*binomial(2*n-2,n-1)*(n+1)^(n-1);
end proc:
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Array[(1/#) Binomial[2 # - 2, # - 1] (# + 1)^(# - 1) &, 17] (* Michael De Vlieger, Jan 28 2020 *)
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
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).
- E. A. DeWitt, Identities Relating Schur s-Functions and Q-Functions, Ph.D. thesis, University of Michigan, 2012, 73 pp.
- A. H. Morales, I. Pak, G. Panova, Hook formulas for skew shapes III. Multivariate and product formulas, arXiv:1707.00931 [math.CO], 2017.
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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);
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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)]
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
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.
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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 *)
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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
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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)]
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
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).
- J. S. Kim and S. Oh, The Selberg integral and Young books, arXiv:1409.1317 [math.CO], 2014.
- J. S. Kim and S. Oh, The Selberg integral and Young books, J. Combin. Theory Ser. A 145 (2017), 1-24.
- A. H. Morales, I. Pak, G. Panova, Hook formulas for skew shapes III. Multivariate and product formulas, arXiv:1707.00931 [math.CO], 2017.
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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);
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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 *)
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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)]
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
For n = 3 there are a(2) = 16 standard tableaux of shape (3,2,1)/(1).
- R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Corollary 7.16.3.
- Alejandro H. Morales, Table of n, a(n) for n = 0..22
- A. H. Morales, I. Pak and G. Panova, Asymptotics of the number of standard Young tableaux of skew shape, arXiv:1610.07561 [math.CO], 2016; European Journal of Combinatorics, Vol 70 (2018).
- A. H. Morales, I. Pak and G. Panova, Hook formulas for skew shapes II. Combinatorial proofs and enumerative applications, arXiv:1610.04744 [math.CO], 2016; SIAM Journal of Discrete Mathematics, Vol 31 (2017).
- A. H. Morales, I. Pak and M. Tassy, Asymptotics for the number of standard tableaux of skew shape and for weighted lozenge tilings, arXiv:1805.00992 [math.CO], 2018.
- A. H. Morales and D. G. Zhu, On the Okounkov--Olshanski formula for standard tableaux of skew shapes, arXiv:2007.05006 [math.CO], 2020.
- H. Naruse, Schubert calculus and hook formula, talk slides at 73rd Sém. Lothar. Combin., Strobl, Austria, 2014.
- I. Pak, Skew shape asymptotics, a case-based introduction, 2020.
- Jay Pantone, File with list of n, a(n) for n = 0..438 (warning: file size is 100MB)
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).
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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);
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