  A sieve is constructed for twin primes at distance 4, which are of the form
3(2m+1)+/-2, and are characterized by their twin-4 rank 2m+1. It has no parity
problem. Non-ranks are identified as all other odd numbers and counted using
odd primes p>=5. Twin-4 ranks and non-ranks make up the set of odd numbers.
Regularities of non-ranks allow gathering information on them to obtain a
Legendre-type sum for the number of twin-4 ranks. Due to considerable
cancellations in it, the asymptotic law of its main term has the expected form
and magnitude of its coefficient.
