I am trying to define a function in terms of a solution of dsolve. I initially tried the following method:

I defined my function as:
a := 10; ode := diff( n(t), t ) + a*n(t);

Then I solve it using dsolve and store it as a function:
f:= t -> dsolve( ode, n(0) = 10);

This was syntactically wrong so I tried:
f:= t-> rhs( dsolve( ode, n(0) = 10) );