

A260040


Triangle read by rows giving numbers H(n,k), number of classes of twintreerooted maps with n edges whose root bond contains k edges.


2



1, 8, 1, 72, 15, 1, 720, 190, 24, 1, 7780, 2345, 415, 35, 1, 89040, 29127, 6384, 798, 48, 1, 1064644, 367248, 93324, 15162, 1400, 63, 1, 13173216, 4708344, 1332528, 261708, 32400, 2292, 80, 1, 167522976, 61343667, 18829650, 4271652, 657198, 63690, 3555, 99, 1, 2178520080, 811147590, 265116720, 67358500, 12269312, 1506615, 117040, 5280, 120, 1
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

See Mullin (1967) for precise definition.
The sequence 1, 8, 72, 720,... in the first column has the same values as in A260039.


LINKS



FORMULA

(k+1)*T(n,k) = A260039(n,k), n>=1, 0<=k<n. [Mullin Eq. (7.1)]
Conjecture: T(n,n3)= (n+1)*n*(5*n^2+7*n+6)/12 = 72, 190,.... for n>=3.  R. J. Mathar, Jul 22 2015


EXAMPLE

Triangle begins:
1,
8,1,
72,15,1,
720,190,24,1,
...


CROSSREFS



KEYWORD



AUTHOR



STATUS

approved



