%I A056328
%S A056328 0,0,0,1,6,37,183,877,3930,17185,73095,306361,1267266,5198557,21182343,
%T A056328 85910917,347187210,1399451545,5629911015,22616256721,90754855026,
%U A056328 363890126677,1458172596903,5840531635357,23385650196090
%N A056328 Number of reversible string structures with n beads using exactly four 
               different colors.
%C A056328 A string and its reverse are considered to be equivalent. Permuting the 
               colors will not change the structure.
%D A056328 M. R. Nester (1999). Mathematical investigations of some plant interaction 
               designs. PhD Thesis. University of Queensland, Brisbane, Australia.
%F A056328 A056323(n)-A001998(n-1).
%Y A056328 Cf. A056311.
%Y A056328 Sequence in context: A047670 A129552 A056338 this_sequence A156185 A057418 
               A001419
%Y A056328 Adjacent sequences: A056325 A056326 A056327 this_sequence A056329 A056330 
               A056331
%K A056328 nonn
%O A056328 1,5
%A A056328 Marks R. Nester (nesterm(AT)dpi.qld.gov.au)