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 | 6 |
| 3 | 39 |
| 4 | 284 |
| 5 | 2205 |
| 6 | 17730 |
| 7 | 145635 |
| 8 | 1213560 |
| 9 | 10218105 |
| 10 | 86717630 |
| 11 | 740526303 |
| 12 | 6355522068 |
| 13 | 54771976597 |
| 14 | 473667151482 |
| 15 | 4108390253595 |
| 16 | 35725327438320 |
| 17 | 311346430241265 |
| 18 | 2718678371881590 |
| 19 | 23780515097337495 |
| 20 | 208330621395422220 |
| 21 | 1827615453799100301 |