code: public <T> DataSetBuilder sequence(String column, T initial, UnaryOperator<T> step) {
      ensureArgNotNull(initial);
      ensureArgNotNull(step);
      return set(column, new StdSeqFiller<T>(initial, step));
    }
docs: Set a sequence filler using a step-function.
  
  <p>
  The sequence of values generated by the filler starts
  with the specified initial value, and subsequent values
  are generated using the step function which takes as input the previous value.
  The sequence will then be
  <code>s(0), s(1), ...</code> where <code>s(0) = initial</code>
  and <code>s(n+1) = step.apply(s(n))</code> for
  all <code>n &gt;= 0</code> .
  </p>
  
  @param <T> Column datum type.
  @param column Column name.
  @param initial Initial value.
  @param step Step function.
  @return The builder instance (for chained calls).
  @see #sequence(String, IntFunction)