perplexus.info :: Numbers : More Consecutive Semiprimes

More Consecutive Semiprimes (Posted on 2009-09-08)

Consider the series of semiprimes. Now consider the series of numbers representing the Sum Of Digits (SOD) of each semiprime.

(1.) How many times does the number '9' occur, and why?

(2.) What is the smallest semiprime that has the same SOD as the next consecutive semiprime? or prove that there is no pair of consecutive semiprimes that have the same SOD.

No Solution Yet Submitted by Larry

No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)

Puzzle Answer

| Comment 5 of 6 |

(1) S=9. The number 9 occurs only once.

(2) There are four 3-digit semiprime pairs. These are:

(146, 155), (226, 235), (278, 287), (346, 355)

Edited on January 7, 2024, 12:06 pm

Posted by K Sengupta on 2023-12-12 06:03:09

Please log in:

Login:
Password:
Remember me:

Sign up! \| Forgot password

Search:

Search body:

Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (10)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:


perplexus dot info