# Q. about triangle A106239 (graphs with unicyclic components)

webonfim webonfim at bol.com.br
Tue Feb 26 05:14:14 CET 2008

```Dear seqfans,

Since T(n,m) = number of graphs on n labeled nodes with m unicyclic components,
we can assume that n >= 1, and 1 =< m <= n, considering that a graph of n vertices can
have from 1 to n connected components. So the values of T(n,m) are:
T(1,1),T(2,1),T(2,2),
,T(k,1),T(k,2),
,T(k,k).   Where n <= k.
It is reasonable to put these values as the lower left triangle:
T(1,1),
T(2,1),T(2,2),

T(k,1),T(k,2),
,T(k, k)
So I thank that A106239 always will be viewed as a lower left triangle. But this is not true.
Consider for example that when we click on the link <table> in a sequence entry, we can see this
sequence as a triangular array, or a square array, or an upper right triangle, but not as a lower
left triangle!
In my opinion this can cause mistakes in the interpretation of sequences.
In the A106239 case, perhaps a commentary like "the sequence is to be read as a lower left triangle. Triangle begins with subscripts (1,1)
0,
0,0,
1,0,0,
15,0,0,0,
222,0,0,0,0,
3660,10,0,0,0,0,
68295,525,0,0,0,0,0,"
makes easier to understand what A106239 is showing.
What do you think?
Any suggestion about table formatting issues?

Thanks, Washington
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