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 | 2 |
| 3 | 9 |
| 4 | 42 |
| 5 | 237 |
| 6 | 1548 |
| 7 | 11547 |
| 8 | 97020 |
| 9 | 907821 |
| 10 | 9369270 |
| 11 | 105785433 |
| 12 | 1297533006 |
| 13 | 17185285377 |
| 14 | 244486594296 |
| 15 | 3718854770571 |
| 16 | 60235136112024 |
| 17 | 1035153878216121 |
| 18 | 18813475216226250 |
| 19 | 360561490742947113 |
| 20 | 7267670240507621010 |