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 A056275 #10 Jan 18 2022 14:40:55
%S A056275 1,1,4,13,50,181,714,2780,11046,43895,175274,699875,2798250,11188191,
%T A056275 44747380,178970560,715860650,2863365834,11453377194,45813202675,
%U A056275 183252461532,733008625151,2932033104554,11728127521060,46912504507000,187649998452735,750599971438464
%N A056275 Number of primitive (aperiodic) word structures of length n using a 4-ary alphabet.
%C A056275 Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same structure.
%D A056275 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 A056275 a(n) = Sum_{d|n} mu(d)*A007581(n/d-1).
%Y A056275 Cf. A008683, A054719.
%K A056275 nonn
%O A056275 1,3
%A A056275 _Marks R. Nester_