设s(x)=x*x^(1/x);r(x)=圆形(s(x));
a(1)=2:
s(1)=1,
s(2)=2.82842712474619。。。;
r(1)=1,
r(2)=3,
r(2)-r(1)=2;
a(2)=4:
s(3)=4.32674871。。。,
s(4)=5.6568542。。。;
r(3)=4,
r(4)=6,
r(4)-r(3)=2;
...
a(19)=108254817:
s(108254816)=108254834.9999999422。。。,
s(108254817)=108254835.5000000346。。。;
r(108254816)=108254834,
r(108254817)=108254836,
r(108254817)-r(1082548016)=2。