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Yes, ratcoeff is a bit confused by taylor expansions at infinity:

qq: taylor(sum((i-3+100)*x^(i-3),i,0,5),x,inf,10)

=> 102*x^2+101*x+100+99/x+98/x^2+97/x^3 + ...

makelist(ratcoeff(qq,x,i),i,-3,4) =>

=> [0, 102, 101, 100, 99, 98, 97, 0]

In other words, it treats the 1/x^2 as the ratcoeff(...,x,2) term.

So the workaround is to negate the power... but of course that will become exactly wrong when the bug is fixed....