[igraph] Network with a Bifurcation

[Lorenzo Isella]

Dear All,
I have not used the igraph library (R bindings) in a while, so please
bear with my question.
I need to generate a network (undirected, a single connected
component, no node has a link with itself and all the links have the
same weight) with a rather simple topology: imagine a central node
which has a 3 first neighbour. From this central node, 3 "chains"
(let's say for now all of the same length) of
nodes stem (i.e. every other node has two neighbours apart from the
three terminal nodes having each one a single neighbour).
For a simple illustration of what I have in mind, have a look at

https://dl.dropboxusercontent.com/u/5685598/network-sketch.pdf

Any suggestion about how to do this, preferably in R, would help me a
lot.
Many thanks

Lorenzo