I'm a 42-year-old near high school failure that barely passed any math class and recently I've been on a kick watching videos before bed based around maths and interesting numbers, formulaes, conjectures, etc. Last night I had a dream that I discovered an interesting math sequence/phenomenon. I figured that any odd number other than 5 when multiplied by 3 and the corresponding results are multiplied by 3 it would result in a series number with a final number that would be transposition of 3971.

EXAMPLE:

1*3=3
3*3=9
9*3=27
27*3=81

81*3=243
243*3=729
729*3=2187
2187*3=6561

I have a feeling this has already been discovered or already known about and, if it has been, I would love to know what it's called.