What will replace the question mark (?) in the following series?1, 3, 9, 39, 249, 2559, ?.

The pattern in the series is as follows:

• From 1 to 3, multiply by 2 and add 1 (1*2 + 1 = 3)
• From 3 to 9, multiply by 3 and add 0 (3*3 + 0 = 9)
• From 9 to 39, multiply by 4 and subtract 1 (9*4 - 1 = 35)
• From 39 to 249, multiply by 6 and add 9 (39*6 + 9 = 243)
• From 249 to 2559, multiply by 10 and add 109 (249*10 + 109 = 2599)

So, the pattern seems to be alternating between adding and subtracting, with the multiplier increasing by 2 each time and the number to be added or subtracted increasing by 1 each time.

Following this pattern, the next step would be to multiply by 12 and subtract 111. So, the number that would replace the question mark would be 2559*12 - 111 = 30609.