Start with a string that's roughly what you want. Base 58 decode it. Delete the last 4 bytes, call the remaining bytes s. Hash s twice with SHA-256. The first four bytes of that are your checksum. Append the checksum to s and base 58 encode it.
Thanks! Worked for me. 12345678912345678912345678913HPoG2
Dang! Nearly one whole bitcoin in that address. Such a waste. Someone needs to make a quantum computer to figure out the private key and put that money to some use! x.x
There's even more in this one: 1111111111111111111114oLvT2
Some algorithms apparently think that the RIPEMD-160 of their public keys is zero... Tsk-tsk.