[questerzen]

I added division and brackets. This gets every number up to 5397, with only about 400 numbers still missing overall (<5%), but run time goes up to 40 minutes.

Potentiation is a problem though (particularly when combined with brackets) as Python becomes impossibly slow using bignums. (I estimate it will take several days of compute time to test all 250 million possibilities, unless I put some effort into speeding it up significantly.) But at least it would prove definitively whether 10958 is possible.

If the only goal were to search for a solution to 10958 though, it should be fairly straightforward to re-order the search in approximately ascending order of compute cost so that if a simple solution exists it will be found quickly.