What is mean of "any three consecutive digits"?

Posted by

stat958 30 Jul 2013 12:52

" Pasha calls an integer a threeprime number if any three consecutive digits of this integer form a three-digit prime number"?

For example,if a number a1a2a3a4, a1a2a3 is a prime number ,the number a2a3a4 must be a prime number?? yes or no, please help me! thank you !

Re: What is mean of "any three consecutive digits"?

Posted by

mjolner 11 Aug 2013 12:09

yes.

In general:

For an n-digit number = a(1)a(2)a(3)a(4)...a(n-1)a(n)

define p(i) = 3-digit number a(i)a(i+1)a(i+2) where 1 <= i <= n-2.

Then each p(i) has to be a prime number *AND* for each p(i) holds: 100 <= p(i) <= 999

*Edited by author 11.08.2013 12:11*