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 | 0 |
| 2 | 5 |
| 3 | 30 |
| 4 | 205 |
| 5 | 1380 |
| 6 | 9305 |
| 7 | 62730 |
| 8 | 422905 |
| 9 | 2851080 |
| 10 | 19221005 |
| 11 | 129581430 |
| 12 | 873593605 |
| 13 | 5889468780 |
| 14 | 39704780705 |
| 15 | 267676028130 |
| 16 | 1804580072305 |
| 17 | 12165860574480 |
| 18 | 82018063808405 |
| 19 | 552937685722830 |
| 20 | 3727716433379005 |