A091511 Number of n X n X n 3-D matrices over symbol set {1,...,n} equivalent under any permutation of rows, columns, stacks or the symbol set.

1, 1, 30, 5887172299, 1025638889935309161425800069552344, 11337715575060644543768059040620852798601554512475786008052416860406653219312996

Offset: 0

Author

Christian G. Bower, Jan 16 2004

Keywords

• nonn

Links

• Philip Turecek, Table of n, a(n) for n = 0..8

Crossrefs

Cf. A091058, A091510.

Programs

Sage

Pol. = InfinitePolynomialRing(QQ)
@cached_function
def Z(n):
    if n == 0: return Pol.one()
    return sum(x[k]*Z(n-k) for k in (1..n))/n
@cached_function
def monprod(M):
    p = Pol.one()
    V = [m.variables() for m in M]
    T = cartesian_product(V)
    for t in T:
        r = [Pol.varname_key(str(u))[1] for u in t]
        j = [Pol(M[u[0]]).degree(u[1]) for u in enumerate(t)]
        lcm_r = lcm(r)
        p *= x[lcm_r]^(prod(r)/lcm_r*prod(j))
    return p
@cached_function
def pol_isotop(n,k):
    P = Z(n)
    p = Pol.zero()
    coeffs = P.coefficients()
    mons = P.monomials()
    C = cartesian_product(k*[mons])
    Csorted = [tuple(sorted(u)) for u in C]
    Cset = set(Csorted)
    for c in Cset:
        p += Csorted.count(c)*prod([coeffs[mons.index(u)] for u in c])*monprod(c)
    return p
@cached_function
def rule_sub(r,m):
    D = 0
    for d in divisors(r):
        try: D += d*m.degrees()[-d-1]
        except: break
    return D
def a(n,k=3):
    P = Z(n)
    coeffs = P.coefficients()
    Q = pol_isotop(n,k)
    inds = [Pol.varname_key(str(u))[1] for u in Q.variables()]
    p = 0
    for mon in enumerate(P.monomials()):
        m = Pol(mon[1])
        p += coeffs[mon[0]]*Q.subs({x[i]:rule_sub(i,m) for i in inds})
    return p
# Philip Turecek, Jun 17 2023

Formula

a(n) = Sum_{1*s_1+2*s_2+...=n, 1*t_1+2*t_2+...=n, 1*u_1+2*u_2+...=n, 1*v_1+2*v_2+...=n} (fixA[s_1, s_2, ...;t_1, t_2, ...;u_1, u_2, ...;v_1, v_2, ...]/ (1^s_1*s_1!*2^s_2*s_2!*... *1^t_1*t_1!*2^t_2*t_2!*... *1^u_1*u_1!*2^u_2*u_2!*... *1^v_1*v_1!*2^v_2*v_2!*...)) where fixA[...] = Product_{i, j, k>=1} ( (Sum_{d|lcm(i, j, k)} (d*v_d))^(s_i*t_j*u_k *lcm(i, j, k)/(i*j*k))).

a(n) asymptotic to n^(n^3)/(n!^4).

Extensions

a(2) corrected by Philip Turecek, Jun 13 2023