Art, the mail carrier delivers mail to the 19 houses on the east side of a street.

Art notices that:
(i) No two adjacent houses ever get mail on the same day, and:
(ii) There are never more than two houses in a row that get no mail on the same day.

How many distinct patterns of mail delivery are possible?

Please see my revised post.

Posted by Ady TZIDON on 2014-09-05 04:08:58