The sequence of locations in the Pokemon Blue/Red town map (if you just keep pressing the up button) is:

1. Pallet Town

2. Route 1

3. Viridian City

4. Route 2

5. Viridian Forest

6. Diglett's Cave

7. Pewter City

8. Route 3

9. Mt. Moon

...

43. Route 22

44. Route 23

45. Victory Road

46. Indigo Plateau

47. Power Plant

The entire sequence matches the order in which you encounter each of these areas in the normal course of gameplay, with the exception of Diglett's Cave, which you don't normally encounter until later in the game.

Is it possible to access Diglett's cave in the sequence described by the Town Map?