# Equilibrium index

From Fōrmulæ wiki

This page is the answer to the task Equilibrium index in the Rosetta Code.

### Description (from Rosetta Code)

An equilibrium index of a sequence is an index into the sequence such that the sum of elements at lower indices is equal to the sum of elements at higher indices.
For example, in a sequence :
3 is an equilibrium index, because:
6 is also an equilibrium index, because:
(sum of zero elements is zero) 7 is not an equilibrium index, because it is not a valid index of sequence .
Write a function that, given a sequence, returns its equilibrium indices (if any). Assume that the sequence may be very long. |

### Program

### Case 1.

In Fōrmulæ, indexes are 1-based so the output of this program will be shifted up by one compared to solutions in languages with 0-based arrays.