The pattern 000000a9 is just in presentation - I counted the occurrences of different bytes in that position (also misled by the apparent pattern, where many lines in a row would have the same 4th byte), and each possible value is present more or less equally often.

It seems like it's just sha1.

EDIT: however, 3.5 million hashes start with 5 zeroes, which is way too many for just coincidence. Possibly they used multiple hash functions?