Treble (in math) is a verb meaning to make 3 times larger (multiply by 3). So each number in the sequence is found by multiplying the previous number by 3.
So the sequence that you're interested in is {1,3,9,27,81}
1, 3, 9, 27, 81
H
1,2,3,4
1,3,9,27,81
1.
2
223
????
3
81
243
It is 3 followed by 1
25, 36, 49, 64, 81, 100...
-375
81
243
81
243
81 is a single 2-digit number. A single number cannot define a sequence.
81
9, 81, 6561, 43046721, ...This would be the sequence 9^(2^(n-1))
It is 3 followed by 1
3-1-.33 repeating
they are all squares - 1², 2², 5², 6², 7², 9²
81 Each number is 3 x the previous number. So, 3 x 27 = 81.
25 36 49 64 81 100 121 144