SpecialFunctions.gamma( ... , ... ) causes error

[Bumblebee00]

Some function needs to be symbolically registered?

julia> integrate(exp(-r^2/2)*r^n,r)
ERROR: MethodError: no method matching gamma(::SymbolicUtils.BasicSymbolicImpl.var"typeof(BasicSymbolicImpl)"{…}, ::SymbolicUtils.BasicSymbolicImpl.var"typeof(BasicSymbolicImpl)"{…})
The function `gamma` exists, but no method is defined for this combination of argument types.

same as

julia> @syms y
julia> SymbolicUtils.gamma(y,y)
ERROR: MethodError: no method matching gamma(::SymbolicUtils.BasicSymbolicImpl.var"typeof(BasicSymbolicImpl)"{…}, ::SymbolicUtils.BasicSymbolicImpl.var"typeof(BasicSymbolicImpl)"{…})
The function `gamma` exists, but no method is defined for this combination of argument types.