History of Chebyshev polynomials of the second kind $U_n$

   comment-orthogonal: The $U_n$ are orthogonal with respect to the inner product $\langle     f,g\rangle = \int_{-1}^1 f(x)g(x)(1-x^2)^{1/2} dx$.+  comment-dickson: The Dickson polynomials of the first kind HREF{Dickson_polynomials_of_the_first_kind}+    are to $T_n$ what the Dickson polynomials of the second kind are to these; only+    the first kind is tabulated here. Formulas:   formula-recurrence: $U_0(x) = 1$,  $U_1(x) = 2x$,  and $U_{n+1}(x) = 2x U_n(x)-U_{n-1}(x)$