Opened 9 years ago

Last modified 9 years ago

## #13516 closed defect

# prime_powers doesn't work with start very well — at Initial Version

Reported by: | kcrisman | Owned by: | was |
---|---|---|---|

Priority: | major | Milestone: | sage-5.6 |

Component: | number theory | Keywords: | beginner |

Cc: | was | Merged in: | |

Authors: | Reviewers: | ||

Report Upstream: | N/A | Work issues: | |

Branch: | Commit: | ||

Dependencies: | Stopgaps: |

### Description

See this sage-support thread.

In Sage 5.3, the function prime_powers behaves a little strange: sage: prime_powers(4,10) [4, 5, 7, 8, 9] # As expected sage: prime_powers(5,10) [7, 8, 9] # 5 isn't a prime power anymore??? # And now things become even worse: sage: prime_powers(7,10) --------------------------------------------------------------------------- IndexError Traceback (most recent call last) /home/mueller/<ipython console> in <module>() /home/mueller/local/sage-5.3/local/lib/python2.7/site-packages/sage/rings/arith.pyc in prime_powers(start, stop) 743 i = bisect(v, start) 744 if start > 2: --> 745 if v[i] == start: 746 i -= 1 747 w = list(v[i:]) IndexError: list index out of range

Yeah, this seems problematic. The code in question is *old*, too, so perhaps there is a more efficient way to do it in the meantime...

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