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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 27 |
| 5 | 199 |
| 6 | 2645 |
| 7 | 34236 |
| 8 | 560742 |
| 9 | 9958754 |
| 10 | 201928954 |
| 11 | 4480386932 |
| 12 | 109410252512 |
| 13 | 2897637649204 |
| 14 | 82974026800132 |
| 15 | 2550731142019568 |
| 16 | 83843131420325008 |
| 17 | 2933465366569951168 |
| 18 | 108862752438362487648 |
| 19 | 4270766898251635808800 |