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}
243
It is 3 followed by 1
25, 36, 49, 64, 81, 100...
'81' Hence 3^(0) = 1 3(1) = 3 3^(2) = 9 3^(3) = 37 3^(4) = 81 3^(5) = 243 3^(n) depending on the numerical position of 'n'.
There are at least three possible answers, consistent with the information given in the question. Short of reading the mind of the person who posed the question, there is no way of determining which of these (or other) solutions is the "correct" one. Answer A: It is 81. The sequence is 1 followed by 2 lots of 9^1, then 3 lots of n^2, then 4 lots of n^3, etc. Answer B: It is 729. The sequence is 1 followed by pairs of powers of n. Answer C: It is 6561. The sequence is 1 followed by a pair of 9s, followed by a pair of 9^2, followed by a pair of (9^2)^2, then ((9^2)^2)^2, etc.
81
243
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
25, 36, 49, 64, 81, 100...