This code was made to ensure there are no collisions in the SHA256 hashes gotten from numerical strings with leading zeros in the range of 0000 000 000 to 9999 999 999.
To execute, this code will need a POSIX-compliant environment (Linux, macOS, perhaps Cygwin) and approximately up to 524 GB of RAM.
OpenSSL
On a memory-optimized current-generation AWS instance on the 64-bit x86 architecture with enough RAM and 64 virtual cores (though the latter are all employed only during a smaller part of the computation), it takes 200 minutes to complete.
No collisions have been identified.