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 A348057 #9 Oct 06 2021 12:49:38 %S A348057 1,4,10,28,74,202,534,1442,3822,10258,27202,72718,192840,514228, %T A348057 1363342,3629316,9619264,25575326,67765590,180001304,476807826, %U A348057 1265567600,3351529410,8890447682,23538665948,62409037914,165202281046 %N A348057 Number of n-step self-avoiding walks on three quadrants of a 2D square lattice. %e A348057 a(2) = 10. Assuming the lower left quadrant is the one removed then a walk of left-down or down-left is not permitted, so the total number of 2-step walks is 4 * 3 - 2 = 10. %Y A348057 Cf. A001411 (four quadrants), A116903 (two quadrants), A038373 (one quadrant), A129700 (half quadrant). %K A348057 nonn,walk %O A348057 0,2 %A A348057 _Scott R. Shannon_, Sep 26 2021