From: utzoo!decvax!harpo!eagle!mhuxt!cbosg!nscs!jpj
Newsgroups: net.math
Title: Re: puzzle
Article-I.D.: nscs.140
Posted: Fri May 28 10:23:20 1982
Received: Sat May 29 06:17:31 1982

Note that the problem is *not* a math problem at all, it is a 
*string* problem!  Given this, you can crank out answers by noticing
that if you choose a value for the right-most digit (say 2) and then
multiply by 2 mod 10 to get the next digit (keeping track of carries
as necessary), when you get to the left-most digit, multiplying it by
2 and comparing it with the digit you started with will tell you if
you have a solution.

What I have found indicates that there are *no* solutions for less
than 18 digits, that the solution at 18 is a string that can be
permuted 8 different ways and that you thus find new solutions at
every string of length n*18 - each time 8 solutions!

These strings were generated on a VAX in under 2 seconds...

n now equals 18

105263157894736842

157894736842105263

210526315789473684

263157894736842105

315789473684210526

368421052631578947

421052631578947368

473684210526315789

	.
	.
	.	

n now equals 90

105263157894736842105263157894736842105263157894736842105263157894736842105263157894736842

157894736842105263157894736842105263157894736842105263157894736842105263157894736842105263

210526315789473684210526315789473684210526315789473684210526315789473684210526315789473684

263157894736842105263157894736842105263157894736842105263157894736842105263157894736842105

315789473684210526315789473684210526315789473684210526315789473684210526315789473684210526

368421052631578947368421052631578947368421052631578947368421052631578947368421052631578947

421052631578947368421052631578947368421052631578947368421052631578947368421052631578947368

473684210526315789473684210526315789473684210526315789473684210526315789473684210526315789


Cheers...
Jim Jenal
BTL/CB