In [latex]LaTeX[/latex], rendering blackboard bold is quite easy in math mode: use \mathbb{}:

[latex]mathbb{ABCDEFGHIJKLMNOPQRSTUVWXYZ}[/latex].

But this does not work with lower case:

[latex]mathbb{abcdefghijklmnopqrstuvwxyz}[/latex]

or with digits: [latex]mathbb{0123456789}[/latex]

a easy contermeasure is to use the command \mathbbm{} provided by the package bbm. This work for all lowercase letters and for some digits, including the 1.