a=1.5 N=3 tau=1: R0 spread 2.07e-40  R2a spread 0.469  R2b spread 0.0584  R3 spread 0.368
a=1.5 N=5 tau=1: R0 spread 5.94e-37  R2a spread 0.000336  R2b spread 3.26e-6  R3 spread 0.034
a=2.2 N=5 tau=2: R0 spread 2.54e-36  R2a spread 0.16  R2b spread 0.0712  R3 spread 0.0694
a=1.5 N=7 tau=2: R0 spread 2.36e-38  R2a spread 0.000382  R2b spread 6.89e-7  R3 spread 0.0882
