OFFSET
1,2
COMMENTS
a(n) = A005195(n) + A236570(n). Proof: Since an at most unicyclic graph is either a forest or a unicyclic graph and since the latter two types of graphs have been enumerated (see A005195, A236570) the enumeration of the at most unicyclic graphs is the sum of the enumeration of the forests and unicyclic graphs, namely, the sum of the sequences A005195 and A236570, where these sequences start for n >= 1, respectively,
1, 2, 3, 6, 10, 20, 37, 76, ...
0, 0, 1, 3, 9, 25, 68 185, ... .
LINKS
E. G. DuCasse, L. V. Quintas, and J. M. Zorluoglu, The At Most Unicyclic Random Graph Process, Mathematics Department, Pace University, New York, No. 1 (2017).
EXAMPLE
For n = 4, a(4) = 6 + 3 = 9 and for n = 5, a(5) = 10 + 9 = 19
CROSSREFS
KEYWORD
nonn
AUTHOR
Louis V QUINTAS, Aug 28 2017
STATUS
approved