Perhaps the pairs 1, 1; 2, 4; 5, 25 are each a number and its square. The number 2 appears to be 1 less than 3 (the number before it). The number 5 appears to be 1 less than 6 (the number before it). The next number in sequence would be the next number in the series 3, 6, __. My first choice for that number would be 9 (an arithmetic series with a difference of 3). My second choice for the next number in sequence would be 12 (a geometric series with a multiplier of 2).
9 is a reasonable guess for the next number.
This assumes the series continues 9 8 64 12 11 121 15 14 196 ...