pandas resample: what is the 3M equivalent of Q

Question

I have a time series, e.g.:

import pandas as pd
df = pd.DataFrame.from_dict({'count': {
  pd.Timestamp('2016-02-29'): 1,  pd.Timestamp('2016-03-31'): 2,
  pd.Timestamp('2016-04-30'): 4,  pd.Timestamp('2016-05-31'): 8,
  pd.Timestamp('2016-06-30'): 16,  pd.Timestamp('2016-07-31'): 32,
}})
df

And can resample it to get counts per Quarter with e.g:

df.resample('Q').agg('sum')

I am trying to do the same with '3M' but no matter what I try, I fail to get the same result, e.g.:

df.resample('3M', closed='right', origin='start',label='right').agg('sum')

gives:

How can I achieve the result of resample('Q') using resample('3M')?