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 A175900 #5 Mar 30 2012 19:01:01
%S A175900 1,2,9,57,411,3150,25274,209719,1784909,15495058,136672624,1221370092,
%T A175900 11034687854,100623850938,924917387599,8560734224711,79717622732369,
%U A175900 746322905220237,7020573752016609,66324819580927731,629004053328092981
%N A175900 Number of lattice paths from (0,0) to (n,n) using steps S={(k,0),(0,k),(1,1)|0<k<=4} which never go above the line y=x.
%Y A175900 Cf. A006318, A175895, A175896
%K A175900 nonn
%O A175900 0,2
%A A175900 _Eric Werley_, Dec 05 2010