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factor((x^15+1)^15-(x^15-1)^15) wrong #1582

Closed rtoy closed 2 days ago

rtoy commented 2 days ago

Imported from SourceForge on 2024-07-04 20:17:06 Created by hebisch on 2005-12-19 01:51:16 Original: https://sourceforge.net/p/maxima/bugs/840

factor((x^15+1)^15-(x^15-1)^15) gives: 30 180 150 120 2 (3 x + 1) (5 x + 150 x + 951 x
90 60 30 + 1828 x + 1059 x + 102 x + 1)

However, the second factor is composite, it is (5*x^60 + 10*x^30 + 1)* (x^120 + 28*x^90 + 134*x^60+ 92*x^30 +1)

This happens on Maxima 5.9.2 on AMD64 using Clisp and on 5.9.1 using gcl (both AMD64 and i386)

rtoy commented 2 days ago

Imported from SourceForge on 2024-07-04 20:17:07 Created by dgildea on 2008-05-25 20:14:17 Original: https://sourceforge.net/p/maxima/bugs/840/#e1a0

Logged In: YES user_id=1797506 Originator: NO

fixed in src/factor.lisp rev 1.17 o nprod: loop structure: was returning after finding factor when no tuples left, rather than continuing to next stage/tloop.

(%i21) factor((x^15+1)^15-(x^15-1)^15) ; (%o21) 2*(3*x^30+1)*(5*x^60+10*x^30+1)*(x^120+28*x^90+134*x^60+92*x^30+1)

rtoy commented 2 days ago

Imported from SourceForge on 2024-07-04 20:17:11 Created by dgildea on 2008-05-25 20:14:17 Original: https://sourceforge.net/p/maxima/bugs/840/#3373