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 | 2 |
| 2 | 6 |
| 3 | 24 |
| 4 | 114 |
| 5 | 612 |
| 6 | 3648 |
| 7 | 23928 |
| 8 | 171534 |
| 9 | 1336416 |
| 10 | 11269476 |
| 11 | 102661188 |
| 12 | 1010777052 |
| 13 | 10778107752 |
| 14 | 124698353796 |
| 15 | 1564720622004 |
| 16 | 21217109251374 |
| 17 | 308917754417352 |
| 18 | 4793408454081468 |
| 19 | 78708576907763868 |
| 20 | 1359861042837591204 |