already solved it,just need to understand somethin

why when its “if not i % 2” should be (2,4,6....8)not (1,5)i dont get it why is it reading those number instead of not reading and ignore

def checkio (array):
  if len (array)== 0:
      return 0
  result = 0
  for i in range (len(array)):
      if not i %2:
          result += array[i]
  return result * array[-1]

print(checkio([1,3,5]))>