Enumeration of Twin Primes and Brun's Constant

Enumeration of the twin primes, and the sum of their reciprocals, to 1.6 × 10^15. An improved estimate is obtained for Brun's constant, B2 = 1.90216 05824 ± 0.00000 00030. Error analysis is presented to support the opinion that the stated error bound represents a 99 % confidence level.