This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A056270 #6 Aug 22 2017 20:53:07 %S A056270 0,0,0,0,120,1800,16800,126000,834120,5102880,29607600,165526200, %T A056270 901020120,4808987400,25292030280,131542740000,678330198120, %U A056270 3474970629480,17710714165200,89904725757000 %N A056270 Number of primitive (aperiodic) words of length n which contain exactly five different symbols. %D A056270 M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2] %F A056270 Sum mu(d)*A001118(n/d) where d|n. %Y A056270 Cf. A000351, A001118, A054720. %K A056270 nonn %O A056270 1,5 %A A056270 _Marks R. Nester_