P

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polynomial in z and y1(z), y2(z), ... and possibly their derivatives and repeated derivatives

listdiffeq

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list containing, for each of y1(z), y2(z), ..., either a linear differential equation it satisfies or a set containing the equation together with initial conditions

list_unknowns

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list of function names  

y

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name; holonomic function name

z

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name; variable of the holonomic function y