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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 34 |
| 5 | 284 |
| 6 | 2698 |
| 7 | 28116 |
| 8 | 314558 |
| 9 | 3726504 |
| 10 | 46310523 |
| 11 | 599691087 |
| 12 | 8051875596 |
| 13 | 111674902936 |
| 14 | 1595269110991 |
| 15 | 23416737953975 |
| 16 | 352551682694096 |
| 17 | 5435771974479840 |
| 18 | 85722307390977058 |
| 19 | 1381216396128765272 |
| 20 | 22718307467700650259 |
| 21 | 381156536404199989205 |