[VA] Short & Sweet Math Challenge #24: "2019 Spring Special 5-tier"

[Valentin Albillo]

 
Hi, Bernd Grubert and Albert Chan:

(04-13-2019 08:01 PM)Bernd Grubert Wrote:  I don't understand the term composite in the context of Tier 2. [...] Please explain what's meant by composite.

With pleasure. In this context composite simply means not prime, i.e., if a number is not prime (thus it can be factored as the product of at least two not necessarily distinct prime factors) then it is considered composite. For instance:

         25 is composite because it's not a prime, as it can be factored as 5 * 5 (two identical prime factors).

         23 isn't composite because it's a prime, as its prime factoring is just itself, 23 (a single prime).

Thanks for your interest. Should you have any further doubts, just tell me.

(04-13-2019 10:35 PM)Albert Chan Wrote:  I recently created nextprime.lua, which is needed for solving Tier 2 puzzle.
[...]
lua> seq=sb_find(7)
lua> loop(10,seq)
7 4801 9547 9601 11311 11317 11941 11953 13033 13327

Nope, this computed sequence for base 7 and all others that follow are incorrect and thus not valid solutions for Tier 2. I think you misunderstood what's actually being asked, which I repeat here with some relevant highlighting for your convenience:

• "Write a program that accepts a base B (2 to 36) and outputs in order those prime numbers N such that S_B(N) is composite and distinct from the previous ones, where S_B(N) is a function which returns the sum of the base-B digits of a given integer N."

Best regards to all.
V.