25384

The answer is only A3 because 125 goes in to 1000 8 times and sequence is all the multiples of eight (note: the sequence misses out one multiple of eight between 2 multiples each time). It's not A0 because that's only odd numbers, it's not A1 because, although it goes up in 4s which 1000 divides into, the numbers in the sequence are 2 bigger than the multiples of 4. It's not A2 because, although that goes up in 8, the numbers in the sequence are 4 more than the multiples of eight. It's not A4 because 1000 doesn't divide by 32 and even if it did, the numbers are 16 more than the multiples of 32. It's not A5 because 64 does not go into 1000, and like before, the numbers in the sequence are 32 more than the multiples of 64. It's not A6 because 128 does not go into 1000, and once again, the numbers are 64 more than the multiples of 128 anyway. Going down in the first column, you will notice that the numbers double each time, so the first number in the sequence for A7 is 128. You will also notice that the number added on to each number in each sequence, is twice the amount of the first number. So it's not A7 for the same reason as all of them, which is that 256 does not go into 1000, and anyway, the numbers in the sequence are 128 more than the multiples of 256.