The function type/SERIES returns true if the value of expr is Maple's SERIES data structure, explained below.

The SERIES data structure represents an expression as a truncated series in one specified indeterminate, expanded at a particular point. A call to the MultiSeries[multiseries] function will always return an object of this type, or 0.

The SERIES structure has nine entries:

the scale (a table, see MultiSeries,scale);

the list of coefficients, which can be SERIES themselves;

the coefficient of the  term, which can be a function of the variable varying more slowly than the expansion variable. It is 0 if the series is exact with respect to its expansion variable (see below);

the common type of its coefficients;

the list of exponents;

the exponent of the  term;

the type of the exponents;

the expansion variable, i.e. the element of the asymptotic basis being used;

the expression being expanded.

SERIES(Scale,[1, -1/6],1,rational,[1, 3],4,integer,_var[x],sin(_var[x]))

SERIES(Scale,[1, 5, 6],0,integer,[-1, 0, 2],infinity,integer,_var[x],1/_var[x]+5+6*_var[x]^2)

SERIES(Scale,[1/(1-_var[x]), 1/(1-_var[x])^2],1,algebraic,[1, 2],3,integer,_var[1/exp(1/x)],-1+1/(1-_var[1/exp(1/x)]/(1-_var[x])))