I have a data frame that looks like this 

```
df = pd.DataFrame({'A': [1,2,3], 'B': [11,12,13]})
df

    A   B
0   1   11
1   2   12
2   3   13

```

I would like to create the following data frame where the columns are a combination of each column-row

```
    A0  A1  A2  B0  B1  B2
0   1   2   3   11  12  13

```

It seems that the pivot and transpose functions will switch columns and rows but I actually want to flatten the data frame to a single row. How can I achieve this?