From the OP:
2019-05-31 - the creator of the "puzzles" creates outgoing transactions with the value of 1satoshi for addresses #65, #70, #75, #80, #85, #90, #95, #100, #105, #110, #115 , #120, #125, #130, #135, #140, #145, #150, #155, #160 with the aim of probably comparing the difficulty of finding a private key for the address from which such a transaction was carried out, and one that There is no transaction.
#64 has never been spent (an outbound transaction), so there's no public key known yet.
If brute force is the only way to creak a P2PKH address with no outbound transactions, then at some point it may become more viable to crack the lower ranges of #160 to #256 (public keys known) than to brute force the "easier" challenges of #156 to #159 (public keys unknown).