When defining a function as a member of a templated class, it is necessary to define it as a templated function.
template class <a_type> void a_class<a_type>::a_function(){...}
I believe your prototypes are incorrect (although I'm noticing pasting template tags in here causes display issues, so it may have been a copy and paste problem)... hence the linker never found a matching template...
Plus you probably need to define
template class Seque<int>;
in the Seque file.
Decent tutorial:
http://www.cprogramming.com/tutorial/templates.html[
^]