Why is the default parameter memo given in the function definition since it's never used/required?

Testing is very much incomplete. My solution tests for a combination of exactly two ( possibly the same ) elements to add up to the target, but passes.

The description clearly specifies any combination of sequence elements, so 0 or more, without reusing elements. ( This follows from the definition of "combination". )

You can assume that all integers in the sequence will all be positive and sequential

This just screams optimisation. However, testing poses no performance requirements at all.

Either just don't mention elements will be sequential ( also, "sequential" is not the correct word - the elements are ( strictly ) "increasing" ), or force solvers to actually use this property of the input. Or, the only option really, unpubish this duplicate ( see below ).

This kata is a duplicate. Please unpublish it.

https://docs.codewars.com/authoring/tutorials/create-first-kata/

1. Random tests are needed.
2. Description most possibly contains logical mistakes.