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 | 2 |
| 2 | 6 |
| 3 | 31 |
| 4 | 227 |
| 5 | 1991 |
| 6 | 19415 |
| 7 | 203456 |
| 8 | 2248356 |
| 9 | 25887400 |
| 10 | 307993016 |
| 11 | 3763786812 |
| 12 | 47032778956 |
| 13 | 598933188956 |
| 14 | 7751562502556 |
| 15 | 101741582076581 |
| 16 | 1351906409905481 |
| 17 | 18159677984049581 |
| 18 | 246298405721739581 |