A number of 50 digits has all its digits equal to 1 except the 26th digit. If the number is divisible by 13, then find the digit in the 26th place.
(In reply to
solution by Charlie)
The mod13 values could be found directly via extended precision provided by UBASIC:
list
10 point 15
20 for I=0 to 49
30 N=N+10^I
40 next
50 print N@13
60 print (10^24)@13
OK
run
11
1
OK
telling us the original mod value and the mod value
for each additional point in the 26th position, then:
? 11111111111111111111111113111111111111111111111111 @ 13
0
OK

With the latter immediatemode print command (the ?) being a check on the answer.

Posted by Charlie
on 20031115 11:46:40 