Problems & Puzzles: Problems Problem 15. Why the Twin Constant is so close to 2/3? Marek Wolf (17/11/98) has proposed the following problem: "Is there any (heuristic) reason why the value of the twin constant C_{2}=0.66016... is so close to 2/3?" C_{2} is called the "twin prime constant" and is the infinite product: C_{2} = Product {1 – 1/(p1)^{2} }, for p>2. Wrench calculated first this constant in 1961. A modern value is this: 0.660161815846869573927812110014555778432623360… See:





