Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Date | Opponent# | Rank# | Site | Result | Attendance |
| --- | --- | --- | --- | --- | --- |
| September 11 | Baylor* | #14 | Ohio Stadium • Columbus, OH | W 21–14 | 88,622 |
| September 18 | at Michigan State | #12 | Spartan Stadium • East Lansing, MI | W 31–10 | 73,483 |
| September 25 | Stanford* | #13 | Ohio Stadium • Columbus, OH | L 20–23 | 89,436 |
| October 2 | Florida State* |  | Ohio Stadium • Columbus, OH | L 17–34 | 89,491 |
| October 9 | Wisconsin |  | Ohio Stadium • Columbus, OH | L 0–6 | 88,344 |
| October 16 | at #15 Illinois |  | Memorial Stadium • Champaign, IL | W 26–21 | 73,488 |
| October 23 | at Indiana |  | Memorial Stadium • Bloomington, IN | W 49–25 | 52,040 |
| October 30 | Purdue |  | Ohio Stadium • Columbus, OH | W 38–6 | 89,341 |
| November 6 | Minnesota |  | Ohio Stadium • Columbus, OH | W 35–10 | 87,666 |
| November 13 | at Northwestern |  | Dyche Stadium • Evanston, IL | W 40–28 | 30,074 |
| November 20 | #13 Michigan |  | Ohio Stadium • Columbus, OH | W 24–14 | 90,252 |
| December 17 | vs. BYU* | #17 | Jack Murphy Stadium • San Diego, CA (Holiday Bowl) | W 47–17 | 52,533 |
Question:
who did ohio state play before indiana on october 23?
Answer:
at #15 Illinois