Ulam's spiral in 159 bytes of Javascript code.



for(x=3,a=148,e=d=f=74,c=2;(x&1?x&2?++e<a-d:--e>d:x&2?++f<a-d-1:--f>d)||++x&3||d--;c++)for(g=0;g<2*a*a;z[g+=c]=1)z[c]||z.getContext("2d").fillRect(2*e,2*f,2,2)

Originally posted here.