_sum for ChebyshevT

Author: dlfivefifty

src/classical/chebyshev.jl

@@ -302,7 +302,7 @@ function _sum(::Weighted{T,<:ChebyshevU}, dims::Int) where T
 end
 
 # Same normalization for T,V,W
-function _sum(::Weighted{T,<:Chebyshev}, dims::Int) where T
+function _sum(::Weighted{T,<:ChebyshevT}, dims::Int) where T
     @assert dims == 1
     Hcat(convert(T, π), Zeros{T}(1,∞))
 end
@@ -318,6 +318,11 @@ function _cumsum(W::Weighted{V, ChebyshevT{V}}, dims::Int) where V
     [cumsum(ChebyshevTWeight{V}()) Weighted(ChebyshevU{V}())] * Diagonal(Vcat(one(V), -inv.(one(V):∞)))
 end
 
+function _sum(::ChebyshevT{T}, dims::Int) where T
+    @assert dims == 1
+    permutedims(vec(Hcat(Vcat(2one(T), -(2one(T)) ./ ((3:2:∞) .* (1:2:∞))), Zeros{T}(∞))'))
+end 
+
 ####
 # algebra
 ####