C 89 , 87 , 82 , 71 bytes

Took xnor's Python solution, and removed the linebreak

p(x,y){for(x=-70*y-x,y=1;x<0;x+=++y*y);printf("%d %d %d",~-y,x/y,x%y);}

0-indexed

z;p(x,y){for(x+=y*70+1,y=z=0;z<x;z+=++y*y);z-=x;printf("%d %d %d\n",y-1,z/y,z%y);}

1-indexed

z;p(x,y){for(x+=~-y*70,y=z=1;z<x;z+=++y*y);z-=x-y;printf("%d %d %d\n",y,z/y,z%y+1);}