K関数
↑ Victor S. Adamchik. PolyGamma Functions of Negative Order
↑ Olivier Espinosa Victor H. Moll. A Generalized polygamma function. Integral Transforms and Special Functions Vol. 15, No. 2, April 2004, pp. 101–115
↑ Weisstein, Eric W. "Hyperfactorial". mathworld.wolfram.com (英語).