This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 15 |
| 5 | 111 |
| 6 | 1131 |
| 7 | 15081 |
| 8 | 253473 |
| 9 | 5220225 |
| 10 | 128886921 |
| 11 | 3749014251 |
| 12 | 126648293391 |
| 13 | 4909623331023 |
| 14 | 216189866951235 |
| 15 | 10718939718977121 |
| 16 | 593865369943409601 |
| 17 | 36520856568972350721 |
| 18 | 2478236630512178688273 |
| 19 | 184588566642520989171795 |
| 20 | 15020141103053997234030351 |