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?
(In reply to
re: a manual count solution by Steve Herman)
Thanks for your correction.
However , the non-recursive method is generally superior to
recursive calculation.
Therefore , my amendment is as follows.
Lets denote by F(n) the number of qualifying sentences, terminating by 1 (which are easily calculated my way).
Then the total T requested for n houses is:
T=F(n) + F(n-1) + F(n-2)
For n=19:
(F19)= 151
(F18)=65+49=114
(F17)= 49+37=86 CALCULATED MY WAY
you will clearly see the benefit , if the street is 119 houses long
(non computer comparison) or 4674689 houses long (computer runtime affected.)
Many sincere thanks for your comment
re(2): a manua etc............. thank you
