Integral of func with 2^(n-1) points
Actual value of integral is  -0.479158
     n         approx. integral
     1             0.905772
     2            -0.020945
     3            -0.361461
     4            -0.449584
     5            -0.471756
     6            -0.477308
     7            -0.478696
     8            -0.479043
     9            -0.479129
    10            -0.479149
    11            -0.479153
    12            -0.479154
    13            -0.479153
    14            -0.479153