RPL mini-challenge - Triangle of Primes (HP-49G/G+,50g)

[Claudio L.]

(07-03-2019 08:00 PM)Gerson W. Barbosa Wrote:  Thank you all for your interest, comments and great contributions!

Wait, wait!

I have 2 more... neither will be winners of anything, just different approaches to those presented before.

The first one is literal translation of the algorithm you just revealed, except 'q' counts with step 1 and NEXTPRIME is done in pairs:

Code:


«
  0 SWAP 2 0 ROT START
    SWAP OVER 0 PICK3
    START
      NEXTPRIME NEXTPRIME
    NEXT
    SWAP 1 + SWAP 
  NEXT
  DROP →LIST 
»

The second one is inspired by the OEIS website, where it shows the highest number is ithPrime(k^2+k+1), so we can just do NEXTPRIME k^2+k+1 times, but keeping (with DUP) just the ones we are interested in, that have an index 'i' of the form 'i^2+i+1':

Code:


«
  0 → 
    i « 1 + DUPDUP *
    + 2 1 ROT
    FOR 'K'
      IF i DUPDUP * +
      1 + K == THEN
        DUP 1 'i' STO+
      END
      NEXTPRIME 
    NEXT
    DROP i →LIST 
  »
»