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