The biggest integer, that I find is 11111212122112, but I do not find any sequense or algo, what can I do???

Edited by author 09.01.2007 00:55

86 digits left for solution
Use long arithmetics

why 86?

my solution has 98 digits.

BTW, does anyone know what is the shortest answer?

My helpprogram work very long... %(((

Edited by author 09.01.2007 08:43

It's very easy to constract answer with length N... (induction)

You mean that it can be solved without long numbers?
I can not find nothing better than divide number on 2^N
on every step

Let H[N]- number under considaration.
Let we define integer K[N]=H[N]/(2^N);
Then K[N+1]=(m*(5^(N-1))+K[N-1])/2; where m=1 or 2;
and K[1]=1;
We solve this reccurence in long arithmetics.
In my module was bad long dividing, thank to this problem
that bug removed now.

I find 2^100 and than add 2^100 until all digits will be 1 and 2... My programm worked 2 hours, but didn't give me the answer!!!

Am I right???

Some number is divisible on 2^n if number which has been written down in his last n digits is divisible on 2^n.

Means we can consistently select digits in the answer.