DAMN IT TOLKIEN, WHAT WERE YOU THINKING

Three Rings for the Elven-kings under the sky,
Seven for the Dwarf-lords in their halls of stone,
Nine for Mortal Men doomed to die,
One for the Dark Lord on his dark throne
In the Land of Mordor where the Shadows lie.

So, that's one ring, then three, then seven, then nine.

1, 3, 7, 9.

Is anyone else irked by this? It's just not a natural progression, dammit. What's with that stupid leap between 3 and 7? How can anyone look at that and not feel, deep down in their soul, that there ought to be an extra FIVE rings somewhere, thereby rendering the sequence 1, 3, 5, 7, 9?

As I see it, 1 3 7 and 9 are numbers, always appearing in old legends and stories. Like 3 brothers, 7 dwarves, etc. I don't know about 5...