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 A056274 #6 Aug 22 2017 20:53:07 %S A056274 1,1,4,12,40,116,364,1080,3276,9800,29524,88440,265720,796796,2391440, %T A056274 7173360,21523360,64566684,193710244,581120880,1743391832,5230147076, %U A056274 15690529804,47071499760,141214768200 %N A056274 Number of primitive (aperiodic) word structures of length n using a 3-ary alphabet. %C A056274 Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same structure. %D A056274 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 A056274 Sum mu(d)*A007051(n/d-1) where d|n and n>0. %Y A056274 Cf. A054718. %K A056274 nonn %O A056274 1,3 %A A056274 _Marks R. Nester_