Black Hole
May contain traces of nut
I don't think this is the one, but I found this:
...here: https://crypto.stanford.edu/pbc/notes/pi/code.html
Code:
int a=10000,b,c=2800,d,e,f[2801],g;main(){for(;b-c;)f[b++]=a/5;
for(;d=0,g=c*2;c-=14,printf("%.4d",e+d/a),e=d%a)for(b=c;d+=f[b]*a,
f[b]=d%--g,d/=g--,--b;d*=b);}
...here: https://crypto.stanford.edu/pbc/notes/pi/code.html