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 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 4 |
| 5 | 65 |
| 6 | 306 |
| 7 | 4207 |
| 8 | 38424 |
| 9 | 573057 |
| 10 | 7753510 |
| 11 | 134046671 |
| 12 | 2353898196 |
| 13 | 47602871329 |
| 14 | 1013794852266 |
| 15 | 23751106404495 |
| 16 | 590663769125296 |
| 17 | 15806094859299329 |
| 18 | 448284980183376078 |
| 19 | 13515502344669830287 |