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 A337907 #6 Oct 01 2020 07:42:45 %S A337907 2,6,48,220,1320,6930,39200,215208,1208340,6754440,38076192,214939296, %T A337907 1218641424,6925848930,39477746880,225542306704,1291514481972, %U A337907 7410367503396,42599109627360,245305128355560,1414839151645920,8172376003368720,47270088643265280,273766119948648000 %N A337907 The number of walks of n steps on the hexagonal lattice that start at the origin and end at the non-adjacent vertex (3/2,sqrt(3)/2). %F A337907 D-finite with recurrence -(n-2)*(n+3)*(n+2)*(n+1)*a(n) +n*(n+2)*(n^2+n+12)*a(n-1) +24*n*(n-1)*(n^2+3*n-1)*a(n-2) +36*n*(n-1)*(n-2)*(n+4)*a(n-3)=0. %e A337907 There are a(2)=2 paths with 2 steps: RU and UR, where R=(1,0), L=(-1,0), U=(1/2,sqrt(3)/2), u=(-1/2,sqrt(3)/2), D=(1/2,-sqrt(3)/2), d=(-1/2,-sqrt(3)/2). %e A337907 There are a(3)=6 paths with 3 steps: UUD, UDU, DUU, RRu, RuR, uRR. %p A337907 # see A337905 %Y A337907 Cf. A002898 (returns to origin), A337905, A337906. %K A337907 nonn,walk %O A337907 2,1 %A A337907 _R. J. Mathar_, Sep 29 2020