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 A056320 #6 Aug 22 2017 20:53:08 %S A056320 0,0,0,12,120,780,4212,20412,93360,409260,1749780,7338000,30394560, %T A056320 124700928,508291692,2061586800,8332140720,33585682920,135116412660, %U A056320 542785390680,2178110585388,8733343485120 %N A056320 Number of primitive (aperiodic) reversible strings with n beads using exactly four different colors. %C A056320 A string and its reverse are considered to be equivalent. %D A056320 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 A056320 sum mu(d)*A056311(n/d) where d|n. %Y A056320 Cf. A056315. %K A056320 nonn %O A056320 1,4 %A A056320 _Marks R. Nester_