A correctly defined sum requires a summand and the index or index range of summation. This error occurs when one of these arguments is not provided.

Note: As a result of updates made in Maple 15, this error message appears in Maple 14 and earlier versions.

Example 1

In the following example, it is unclear whether the argument $i$represents the summand or the index.

Solution:

For this example, we assume the intention was for the summand and index to both be $i\.$ You must explicitly state both arguments for sum.

Example 2

In the following example, attempting to sum more than one summand at a time results in an error.

Solution:

To sum more than one summand at at time, use the map command.

Example 3

In the following example, attempting to calculate the sum of $i\+j$over both index variables results in an error. This statement is not well-defined.

Solution:

Depending on the interpretation, one possible solution is to express the sum in the following manner:  if the indices are meant to be sequenced individually, then the following statement corrects the error and produces the intended result.

Otherwise, if the indices are meant to be sequenced in tandem, then the following statement corrects the error and produces the intended result.

 eval,  map, sum