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 | 18 |
| 4 | 261 |
| 5 | 3411 |
| 6 | 42048 |
| 7 | 499131 |
| 8 | 5770611 |
| 9 | 65427678 |
| 10 | 730784601 |
| 11 | 8065910511 |
| 12 | 88170256008 |
| 13 | 956125498671 |
| 14 | 10298661792111 |
| 15 | 110293085617038 |
| 16 | 1175325726682341 |
| 17 | 12470569310694411 |
| 18 | 131813055336390768 |
| 19 | 1388552621823766611 |
| 20 | 14583291094441416411 |
| 21 | 152746593446386647198 |