TIL: powers of 3 sequence has secret property.
That's minimal sequence, any arithmetic operations with any subsequence gives unique result:
...
4=1+3
5=-1-3+9
6=-3+9
7=1-3+9
...
3159=243+729+2187
oeis.org/A000244
is that well-known?
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you're right, looks like balanced ternary system
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