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 A139772 #9 Feb 16 2022 23:22:41 %S A139772 2,64,37160,378875648,67433401509980,209087783283413477232, %T A139772 11281654633785546173131745084 %N A139772 Number of linear trimer coverings of a 3n X 3n square. %D A139772 J. Van Craen, The residual entropy of rectilinear trimers on the square lattice at close packing, J. Chem. Phys. 63 (1975) 2591-2596. %Y A139772 Cf. A004003. %K A139772 nonn,more %O A139772 1,1 %A A139772 _Steven Finch_, May 20 2008 %E A139772 Name corrected and a(6)-a(7) from _Andrew Howroyd_, Feb 16 2022