Primes of the form 10^n+-n
- 10^n+n is prime for n=1, 9, 69, 313 and 451.
10^n-n is prime for n=3, 23, 171, 903 and in both cases no other values
likely to be found in a significant amount of time (n checked through 8
thousand). This may be already known, I have not checked.