First of all, a public key is not the same as a public key hash. You can find out the public key hash, which is simply RIPEMD160(SHA256(pubkey)) for any address, simply be decoding the address back from Base58 back in to hex and striping off the network byte and checksum. The public key hash for 16jYMfASQ4ngejMcVUoAjEBvq9HKnc6UX2 is 3EE4462D45A65A3CBE9E3DD19780C0A29C4E39D3.

In terms of getting the public key of 16jYMfASQ4ngejMcVUoAjEBvq9HKnc6UX2, the answer is you can't right now. The address has only received coins - it has not spent them. You need a transaction where coins are spent from an address for that address's public key to be part of the signature. Until that happens (or a message is signed from that address) then its public key remains unknown.