arms in the trial, the
sample size per treatment arm (assumed equal) and the timing of adding
arms in terms of patients recruited to the trial so far.</p>
<ul>
<li><code>num_arms</code> Number of treatment arms in the trial</li>
<li><code>n_arm</code> Sample size per arm (assumed equal)</li>
<li><code>d</code> Vector with timings of adding new arms in terms of
number of patients recruited to the trial so far (of length
<code>num_arms</code>)</li>
<li><code>period_blocks</code> - number to multiply 