# import necessary libraries
import pandas as pd
import numpy as np
# define your series and bins
bins = 10
series = pd.Series([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,\
12, 13, 14, 15, 16, 17, 18, 19, 20])
# use np.histogram method
hist, bin_edges = np.histogram(series, bins=bins)
# create a dataframe to better display the results
result_df = pd.DataFrame({'bin_lower': bin_edges[:-1],
'bin_upper': bin_edges[1:],
'frequency': hist})
# display result
print(result_df)