
COMMENTS

The alphabet may be any set of size 4 (GF(4), Z/4Z, etc.) so there is no requirement of linearity.
a(6) is known to be in the range [164179], and a(7) in the range [512614].


LINKS

Table of n, a(n) for n=1..5.
N. J. A. Sloane, Challenge Problems: Independent Sets in Graphs
R. Barden, N. Bushaw, C. Callison, A. Fernandez, B. Harris, I. Holden, C. E. Larson, D. Muncy, C. O'Shea, J. Shive, J. Raines, P. Rana, N. van Cleemput, B. Ward, N. WilcoxCook, The Graph Brain Project & Big Mathematics, research paper, 2017.
Galina T. Bogdanova, Andries E. Brouwer, Stoian N. Kapralov and Patric R.J. Ostergard, ErrorCorrecting Codes over an Alphabet of Four Elements, Designs, Codes and Cryptography 23 (2001) 333342.
Oleksandra Yezerska, Sergiy Butenko, The Maximum Clique and Vertex Coloring, Handbook of Heuristics. Springer, Cham, 2018, 131.
