以下t>0
(210526315789473684共t个)=(105263157894736842共t个)*2
(315789473684210526共t个)=(157894736842105263共t个)*2
(421052631578947368共t个)=(210526315789473684共t个)*2
(526315789473684210共t个)=(263157894736842105共t个)*2
(631578947368421052共t个)=(315789473684210526共t个)*2
(736842105263157894共t个)=(368421052631578947共t个)*2
(842105263157894736共t个)=(421052631578947368共t个)*2
(947368421052631578共t个)=(473684210526315789共t个)*2
(105263157894736842共t个)=(052631578947368421共t个)*2
(这个答案要用特别理解,要在首位添上0)
设原数有n+1位,前n位数字组成的数记为a,个位为b.
依题意,(10a+b)*2=10^n*b+a,即(10^n-2)b=19a
因为a,b13,13-6->7,14,14-5>9,18,18-1>17,17-2>15,15-4>11,22-19>3,6,12,24>5,10