Larcombe, Peter J., & Larsen, Mogens E. (2009). The sum 16nΣ2nk=04k( 1/2k)(-1/2k)(-2k 2n-k): A proof of its closed form. Utilitas Mathematica, 79. Retrieved from https://utilitasmathematica.com/index.php/Index/article/view/628