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I am looking for 20 addresses with the above set of prefixes.
Any or all of them? Because combining different prefixes only helps so much. It lowers the difficulty, but it usually only means that the "easiest" ones are found first while there is no time wasted for the most difficult only. E.g. 1panthers59 has a predicted 50% time of 1 year. Its very unlikely that it will be found.
Would you be willing to compute 20 (with a single public key, so you could just leave it running) for .055BTC?
Not a straight answer yet, just noting that I just tested that and yes it will keep going until it finds a key for all prefixes given a single pubkey. There are two possible modes,
-k which just keeps searching for the same prefixes until I stop it manually. This will probably result in dublicated prefixes. Which is a given anyway since you want 20 addresses, but have less prefixes. Without the -k flag it will strike a prefix of the list until it has found all.
If that is too large a risk for you (due to potential variance) then I would be willing to buy computing time on your computer (to generate as many vanity addresses as possible with the above prefixes), and would be willing to pay .055BTC for the following amount of time: ([estimated amount of time to generate one address from the above address]*1.07)*20 // In other words I would be willing to buy the amount of time it is estimated to find 20 addresses, assuming 93% luck.
The thing is there is no 100% time. It could take me 100 years to find an address with the prefix '12', its just very unlikely. From a quick test on the CPU the times to reach the next "step" behave like this.
% stp ttl
50% x x
75% x 2x
80% x/3 2.3x
90% x 3.3x
95% x 4.3x
There is no further prediction above 95%. I managed to get to 98%, but never higher. Would be incredible unlikely anyway. I usually calculate with 75%.
Either way, please provide a PGP signed address to send payment to, along with confirmation of the exact price/terms of sale (if something needs to be adjusted price wise, that is no problem).
Will do lets iron out the details first.
What I can offer is 20 address with any of the below 12 prefixes (with a combined difficulty of 229,244,582,148) with out exact case for a total of 0.0998 BTC.
1camnewton
1superman
1elevenno # not 'zero'
1superbowl
1suprbowl
1panthers1
1panthers59
1nolosses
1lukeeeee
1lukeee59
1tochdown
1winnerso # not 'zero'
1runtable
Since that is almost twice your price I can offer you the same deal but with '1panthers' instead of '1panthers1' and '1panthers59', so 11 prefixes with a combined difficulty of 145,206,698,550 for 0.0312 btc.