VNAF squadron numbering system - odd ones out

The VNAF squadron numbering system was one of the easiest to understand in the world in one way, and one of the most puzzling in the other. Each type of mission within the VNAF was assigned it's own squadron designation in a one hundred sequence or multiple-hundred sequence, ranging from 100 to 900. The mission types were:

Observation	100 sequence (e.g. 116th OS)
Helicopter	200 sequence (e.g. 223rd HS)
Special Mission	300 sequence (e.g. 312th SMS)
Transport	400 sequence (e.g. 417th TS)
Fighter	500 sequence (e.g. 522nd FS)
Amphibious	(not used; plans were abandoned)
Reconnaissance	700 sequence (e.g. 716th RS)
Attack	800 sequence (e.g. 819th AS)
Training	900 sequence (e.g. 918th TRS)

There are a few particularities about this squadron numbering system:

An odd hundreds-number would never be followed by an even number in a squadron number. If the first digit was even, the following two-digit number would be odd. If the first digit was odd, the following two-digit number would be even.

The 522nd Fighter Squadron: 5 is odd, 22 is even. The 819th Attack Squadron: 8 is even, 19 is odd. This rule goes for every VNAF squadron. There was never an 820th Attack Squadron or a 523rd Fighter Squadron. The reason for this practice is unknown to me. It was not implemented on the Wing numbering system. There was a 62nd Tactical Wing, a 64th Tactical Wing, an 82nd Tactical Wing, and an 84th Tactical Wing, a 23rd, 33rd, 43rd, 51st, 53rd, 61st, 63rd, 72nd, 83rd and 92nd Tactical Wing.

It's known that some of the wing numbers date back to when air bases were referred to as "Air Base 63" and that number was used when wings (63rd Wing in this example) were established, simply because that new wing was established on that air base. If anyone knows more about this, please let me know.