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 | 5 |
| 2 | 45 |
| 3 | 419 |
| 4 | 3665 |
| 5 | 30795 |
| 6 | 253137 |
| 7 | 2056059 |
| 8 | 16589761 |
| 9 | 133362635 |
| 10 | 1069841265 |
| 11 | 8572141979 |
| 12 | 68638314785 |
| 13 | 549385589355 |
| 14 | 4396357712337 |
| 15 | 35176668544059 |
| 16 | 281439836584321 |
| 17 | 2251639520143115 |
| 18 | 18013667322023985 |
| 19 | 144111852725650139 |
| 20 | 1152906290230734305 |
| 21 | 9223302635674623915 |