Some numbers remain numbers when turned upside down (using digits 0125689, with no final 0's): 1, 2, 5, 6, 8, 9, 11, 12, … etc

IF a₁=1, a₂=2, a₃=5,... a₈=12,…, etc

a.Evaluate a₁₀₀
b. Evaluate a₁₀₀₀
c. If a_n= 888, what is n?

(In reply to Direct Basic solution by Steve Herman)

1.  map the digits 0123456 to 0123689

Should read : map the digits 0123456 to 0125689 (REPLACE 3 BY 5)

The result was not affected

2...."For example, a(x) = 888,888  
This maps to 666666   Should be This maps to 555555 (REPLACE 6 BY 5),..

3. Convert to base 7 giving 16,806 ...  WRONG

YOU should  Convert from base 7 to decimal  getting 14005 etc...

.and get.the answer. x=84035 for a(x)=888,888 (If I  did not err)

Please edit and check your procedures on puzzle's questions (100,1000,888)  to compare with Charlie's results.

 

Posted by Ady TZIDON on 2014-04-12 09:27:56