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 | 1 |
| 2 | 3 |
| 3 | 21 |
| 4 | 243 |
| 5 | 3933 |
| 6 | 81819 |
| 7 | 2080053 |
| 8 | 62490339 |
| 9 | 2166106509 |
| 10 | 85092601707 |
| 11 | 3735939709989 |
| 12 | 181287330220467 |
| 13 | 9634718677393917 |
| 14 | 556569415611455931 |
| 15 | 34723276781195740437 |
| 16 | 2326773811332029313411 |
| 17 | 166666995789875216053101 |
| 18 | 12708546598923724476443403 |