HP 41C: Fermat Factorization - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Software Libraries (/forum-10.html) +--- Forum: HP-41C Software Library (/forum-11.html) +--- Thread: HP 41C: Fermat Factorization (/thread-1801.html) HP 41C: Fermat Factorization - Gerald H - 07-08-2014 02:06 PM Fermat's factorization method is particularly good for finding large factors of a number, & very poor at finding small factors. For example, for 608,391 (=3^4*7*29*37) the programme finds 777 & 783 almost instantaneously. Consequently the method is most efficient in dealing with the "difficult" case of a composite number having two large prime factors. The number 8616460799 is factorized in 695 s. 1. LBL “FERM” 2. STO 00 3. SQRT 4. INT 5. RCL X 6. RCL Y 7. + 8. 1 9. STO T 10. + 11. STO Z 12. RDN 13. X^2 14. RCL 00 15. – 16. LBL 00 17. X=0? 18. GTO 01 19. RCL Y 20. + 21. 2 22. ST+ Z 23. RDN 24. LBL 02 25. RCL Z 26. – 27. 2 28. ST+ T 29. RDN 30. X>0? 31. GTO 02 32. GTO 00 33. LBL 01 34. RDN 35. X<>Y 36. – 37. 2 38. / 39. RCL 00 40. RCL Y 41. / 42. END RE: HP 41C: Fermat Factorization - Dwight Sturrock - 07-27-2014 01:41 AM Adapted for the HP15C /LE : 1. LBL A 2. STO 0 3. SQRT 4. INT 5. ENTER 6. ENTER 7. + 8. 1 9. STO 4 10. + 11. STO 3 12. RDN 13. X^2 14. RCL 0 15. - 16. LBL 0 17. X=0 18. GTO 1 19. RCL 3 20. + 21. 2 22. STO +3 23. RDN 24. LBL 2 25. RCL 4 26. - 27. 2 28. STO +4 29. RDN 30. TEST 1 (X>0) 31. GTO 2 32. GTO 0 33. LBL 1 34. RCL 3 35. RCL 4 36. - 37. 2 38. / 39. ENTER 40. ENTER 41. RCL 0 42. X<>Y 43. / 44. RTN RE: HP 41C: Fermat Factorization - Ángel Martin - 07-29-2014 06:13 PM (07-27-2014 11:01 PM)Geir Isene Wrote:  Is this method made available as MCODE in one of Angel Martin's modules? Not that I'm aware (and I guess I should know it :-) - I used the MCODE PRIME? function as the basis of the factorization - darn fast if you must know.