series yields wrong result

[dkrenn]

The following was posted on  the public bug reports from the notebook interface by Clemens Heuberger on 1/4/2011 and on  sage-support. In the latter other code examples were posted.

f.series(q,2) for the f defined below yields Order(q^2) which is incorrect, as f.subs(q=0) equals 1 (which is correct).

sage: var('q')
sage: f=(q^13362120470/((q - 1)*(q^5 - 1)*(q^21 - 1)*(q^85 - 1)*(q^341 -
1)*(q^1365 - 1)*(q^5461 - 1)*(q^21845 - 1)*(q^87381 - 1)*(q^349525 -
1)*(q^1398101 - 1)*(q^5592405 - 1)*(q^22369621 - 1)*(q^89478485 -
1)*(q^357913941 - 1)*(q^1431655765 - 1)*(q^5726623061 - 1)) +
1)/(q^7635497409/((q - 1)*(q^5 - 1)*(q^21 - 1)*(q^85 - 1)*(q^341 -
1)*(q^1365 - 1)*(q^5461 - 1)*(q^21845 - 1)*(q^87381 - 1)*(q^349525 -
1)*(q^1398101 - 1)*(q^5592405 - 1)*(q^22369621 - 1)*(q^89478485 -
1)*(q^357913941 - 1)*(q^1431655765 - 1)*(q^5726623061 - 1)) + 1)
sage: f.series(q,2)
Order(q^2)
sage: f.subs(q=0)
1