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 | 3 |
| 3 | 9 |
| 4 | 105 |
| 5 | 306 |
| 6 | 3567 |
| 7 | 10395 |
| 8 | 121173 |
| 9 | 353124 |
| 10 | 4116315 |
| 11 | 11995821 |
| 12 | 139833537 |
| 13 | 407504790 |
| 14 | 4750223943 |
| 15 | 13843167039 |
| 16 | 161367780525 |
| 17 | 470260174536 |
| 18 | 5481754313907 |
| 19 | 15975002767185 |
| 20 | 186218278892313 |
| 21 | 542679833909754 |