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 | 4 |
| 2 | 28 |
| 3 | 208 |
| 4 | 1624 |
| 5 | 13024 |
| 6 | 106336 |
| 7 | 879232 |
| 8 | 7338592 |
| 9 | 61699456 |
| 10 | 521753728 |
| 11 | 4433024512 |
| 12 | 37812715264 |
| 13 | 323603221504 |
| 14 | 2777262164992 |
| 15 | 23893731463168 |
| 16 | 206005885076992 |
| 17 | 1779480850438144 |
| 18 | 15396895523989504 |
| 19 | 133420304211238912 |