Effective Chebyshev theta estimate #
This is the quantitative bridge from the PNTAnd estimate for psi to the
prime-only Chebyshev function theta. It is the analytic input used by the
Mertens partial-summation development.
The medium PNT error for psi transfers to theta, with the standard
sqrt x prime-power correction retained explicitly.
A coarser theta estimate in the form used by partial summation.
The endpoint error in the Abel formula for reciprocal-prime sums.