>Some thoughts about higher sudokus than 3x3:
>
>There is a way to give a rather accurate estimate on the number
>of Nx3-sudokus, when the number R of ways to complete the first
>band is calculated:
when you say Nx3, that's what others usually call N*N x 9 - sudokus
>Let M be the number of column configurations for a Nx3-box that
>do not come in conflict with another fixed Nx3-configuration.
and it doesn't matter which, M is always the same.
So M depends on N alone. So maybe M=CC(N) , CC for column-configurations
>A column configuration is a splitting of the 3N numbers into
>three disjoint sets (S_1,S_2,S_3) of N numbers each. Two such
>configurations (S_1,S_2,S_3) and (T_1,T_2,T_3) are in conflict
>if T_ and S_i have a common element for some i.
I called them G-classes (G for gangster) of a Nx3 box : you are
allowed to permute entries in a Nx1 column or permute the 3 columns.
However you don't allow permuting the columns here
>M is given as the sum of (N ch k)^3 when k runs from 0 to N,
>and where (N ch k) is the binomial function. This is because
>for a given k, there are (N ch k) [ways] to pick k numbers from S_1
>to be in T_2, the rest are in T_3, and so we need k numbers
>from S_2 in T_3 and from S_3 in T_1.
>
>The total number of column configurations for a box is (3N)!/N!^3.
= (3*N ch N) * (2*N ch N) = :CC(N)
>The expected (this is where the calculation turns from being exact
>to an estimation) number of bands that can be found from a given
>sequence of column configurations for each of the N boxes on a band,
>is then
>
>R/[ (3N)!/(n!)^3 ]^N = R * n!^(3N) / (3N)!^N
putting N Nx3-CCs together horizontally to form a Nx3N band
>And so we have the estimate:
>
>- The first band can be created in R ways.
>- Then the second band has M^N configurations, and therefore
> R * M^N * n!^(3N) / (3N)!^N expected rows
(what you mean with rows ?)
expected number of N*3N-bands in the middle per fixed first band
>- And finally, then the third band has one unique configuration,
> and therefore R * n!^(3N) / (3N)!^N expected rows
expected number of N*3N-bands in the third place, per fixed 1st and 2nd bands
>Hence, the expected number of rows is
>
>S(N) = R^3 * M^N * N!^(6N) / (3N)!^(2N)
expected number of grids, multiplying the 3 numbers for the bands
>Some values for N...
>
>N=1:
>R=6 (number of choices for the first row in a 3x3 latin square)
>M=2
>S(1)=12, this is also the exact answer (naturally, since there
> is only one configuration modulo permutations)
>
>N=2:
>R=20 * 6^4 (20 ways to choose the numbers on the first row in
> the first box, 6^4 ways to permute the order on each row in each box)
>M=10
>S(2) = 26542080, the exact answer is 28200960, 17/16 times S(2).
>The estimate is 6.25% from the right answer.
>
>N=3:
>This is what we have been doing here
>R=948109639680 (9!*56*6^6)
>M=56
>S(3) = 6.657e21, as already calculated earlier by others, this is
> only 0.2% from the right answer
yes, looks good !
>N=4:
>R=2273614462643364849254400 (I have just calculated this number,
>confirm it those who wish)
>M=346
>S(4) = 4.267532227e81, I'm sure this is less than 0.1% from the
>right answer
>
>This illustrates how fast the number of NxM-grids grows.
>I have the plans for a program counting the 3x4-grids,
>but I don't know if it can be run in w reasonable amount of time.
>
>As my program counts 3x3-grids in 2.6 seconds, while 3x4 will
>take hours, maybe days, I am more than ever sure about the
>impossibility of finding the number of 4x4-grids.
.. but maybe an estimate, using the same method for 4*16 bands ?
1e300 or 1e400 , that would be a giant difference ;-)
another estimate could probably also be done by Monte-Carlo
randomized generation of bands. That should hopefully confirm
your estimates.
Guenter.
PS. can we do the 416^6 classification program this week ?
I sent PM, but maybe you haven't read it. My email is
sterten@aol.com , or just click on the item below this message