-- If the rule is "triple it and add 2", then the next number is -28 .
-- If the rule is "subtract three times as much as you subtracted last time", then it's still -28 .
-- If the rule is "double it and subtract 2 more than you subtracted last time", then it's -24 .
-- If the rule is "square it and subtract 18 more than you subtracted last time", then it's +56 .
There are many different rules that can generate -2, -4, -10 . . . an infinite number, I think.
We need one more term of the sequence. That would let us see the rule applied twice, and
we could narrow it down and pick the right rule.
The next number in the sequence is 27.
21
The given number sequence is a series of perfect squares: 7^2, 8^2, 9^2, 10^2. Therefore, the next number in the sequence would be 11^2, which is 121.
Consecutive terms in the sequence are found by dividing by 2 and adding 2. Therefore, after the number 10 comes 10/2 + 2 = 7.
20
Each subsequent number in this sequence is 2 less than the previous. It is extremely likely that the next number in this sequence is 2.
I think that the next number in the sequence is 360.
To get the next number in the sequence, you simply multiply by 26*2=1212*2=2424*2=4848*2=96
27
it is 7
58
The single number 21050 does not define a sequence.