Chebyshev polynomial of the second kind U(3,n).

Terms

a(0) =0a(1) =4a(2) =56a(3) =204a(4) =496a(5) =980a(6) =1704a(7) =2716a(8) =4064a(9) =5796a(10) =7960a(11) =10604a(12) =13776a(13) =17524a(14) =21896a(15) =26940a(16) =32704a(17) =39236a(18) =46584a(19) =54796a(20) =63920a(21) =74004a(22) =85096a(23) =97244a(24) =110496a(25) =124900a(26) =140504a(27) =157356a(28) =175504a(29) =194996