There are several different issues. In your first example you write ((1/(1-x1^t)).taylor(x2,1,4).taylor(x1,1,4).coefficient(1/(x1-1))). substitute(x2=1)
Note that contrary to your other examples x2 is not in the expression you expand the series from. A typo? In the second example ((1/(1-x2*x1^t)).taylor(x1,1,4)).coefficient(1/(x1-1)).substitute(x2=1) just look at the series you get, there is no term with 1/(x1-1) so you get 0 as coefficient. In the third example you are looking for the coefficient of s^n with s being a sum. This is not supported generally. Try to substitute the sum before taking the coefficient: sage: ((1/(1-x2*x1^t)).taylor(x2,1,4).taylor(x1,1,4)).substitute(x2==1,x1-1 ==y).coefficient(y) -1/12*(t^6 - t^4)/t^5 Regards, > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
