Problems & Puzzles: Puzzles

Puzzle 491. Sum of any combination is not prime

Anton Vrba  sent the following puzzle:

Add terms to the series 4, 24, 24, 122, 332, 2487, 11847, 40196, 73915, ...

  • 4 is the first composite number
  • 24, 25 are the least two consecutive composite numbers whose sum is not prime
  • 24, 25 and 26 are the least three consecutive consecutive numbers whose sum of any combination is not prime (24+25, 25+26, 24+26 and 24+25+26)
  • 122, 123, 124 and 125 are the least four consecutive composite ......

 

 

 

Contribution came fro, Igor Schein.

***

Igor wrote:

The next 2 numbers are 1078046, 13865665

A few days after he added:

Going one further: 69205020.

***

Farideh Firoozbakht found one more term:

The next two terms are 69205020 & 430480044.

So the first 13 terms of the sequence are:

4, 24, 24, 122, 332, 2487, 11847, 40196, 73915, 1078046, 13865665, 69205020,
430480044.

***

Records   |  Conjectures  |  Problems  |  Puzzles