There is a 6 digit-number consisting of the digits: 1, 1, 2, 2, 3, and 3.
The ones are 1 digit apart, the twos are 2 digits apart, and the threes are 3 digits apart.
What is the number?
3 1 2 1 3 2
1 and 9 are both perfect squares that each consist of only odd digits. Are there any other perfect squares consisting of only odd digits?
Using the digits 1, 2, 3 and 4, find the number of 10-digit sequences that can be written so that the difference between any two consecutive digits is 1.
Examples of such 10-digit sequences are ********** and **********.
