Mazes. & Coprime Grids

[N. J. A. Sloane]

Dear Leroy, Seqfans:

there was an extensive discussion about this while 
I was away.  I'm adding one sequence from it (see below)
but I would like to get others. Would you please
submit them in the usual way?
Thanks!

For example, here is an extract from one of those emails:

> If I'm correct, here are some values for you, other values may take some time
> (or need a smarter program...)
> The first column (or row) is A076220.
> b(n)= 1, 8, 2016, 19611648, ... does not appear in OEIS, nor
> 1,2,2,6,8,6,12,16,16,12,72,432,2016,432,72,...
> bye,
> giovanni.
> 
> (use a fixed font like courier to preserve alignment)
> 
>   |    1       2        3         4       5     6       7        8
> --------------------------------------------------------------------
> 1 |    1        2       6        12      72    72     864     1728
> 2 |    2        8      16       432    2784 35712 2121984 34069248
> 3 |    6       16    2016     23904 7102656
> 4 |   12      432   23904  19611648
> 5 |   72     2784 7102656
> 6 |   72    35712
> 7 |  864  2121984
> 8 | 1728 34069248
> ========================================
> 
Giovanni, would send in that triangle and some rows and cols
as appropriate?

Here is the single one that I have added:

%I A116469
%S A116469 1,1,1,1,4,1,1,15,15,1,1,56,192,56,1,1,209,2415,2415,209,1,1,780,30305,
%T A116469 100352,30305,780,1,1,2911,380160,4140081,4140081,380160,2911,1,1,10864,
%U A116469 4768673,170537640,557568000,170537640,4768673,10864,1,1
%N A116469 Number of spanning trees in an m x n grid read by antidiagonals.
%C A116469 This is the number of ways the points in an m x n grid can be connected to their orthogonal neighbours such that for any pair of points there is precisely one path connecting them
%C A116469 a(n,n) = A007341(n)
%e A116469 a(2,2) = 4, since we must have exactly 3 of the 4 possible connections: if we have all 4 there are multiple paths between points; if we have fewer some points will be isolated from others.
%O A116469 1,5
%Y A116469 Cf A007341.
%K A116469 nonn,tabl
%A A116469 Calculated by Hugo van der Sanden (hv(AT)crypt.org) after a suggestion from Leroy Quet, Mar 20 2006.


Thanks

Neil