Riemann hypothesis - Zeros on the critical line - Gram points

Gram observed that there was often exactly one zero of the zeta function between any two Gram points; Hutchinson called this observation Gram's law. There are several other closely related statements that are also sometimes called Gram's law: for example, (−1)nZ(gn) is usually positive, or Z(t) usually has opposite sign at consecutive Gram points. The imaginary parts γn of the first few zeros (in blue) and the first few Gram points gn are given in the following chart:

Reference 1: .

Reference 2: , , g−1, γ1, g0, γ2, g1, γ3, g2, γ4, g3, γ5, g4, γ6 and g5.

Source: http://en.wikipedia.org/wiki/Riemann_hypothesis