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 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 34 |
| 5 | 250 |
| 6 | 2058 |
| 7 | 18661 |
| 8 | 185695 |
| 9 | 2017527 |
| 10 | 23804069 |
| 11 | 303413813 |
| 12 | 4157895295 |
| 13 | 60989187252 |
| 14 | 953766105164 |
| 15 | 15844435971349 |
| 16 | 278704524938621 |
| 17 | 5175632136205088 |
| 18 | 101198102131888304 |
| 19 | 2078318050691940125 |
| 20 | 44731639502987747576 |
| 21 | 1006917859088311808499 |