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 | 21 |
| 2 | 252 |
| 3 | 2233 |
| 4 | 16170 |
| 5 | 100926 |
| 6 | 560945 |
| 7 | 2837418 |
| 8 | 13266099 |
| 9 | 57994475 |
| 10 | 239170239 |
| 11 | 937026279 |
| 12 | 3507380170 |
| 13 | 12601619226 |
| 14 | 43628951025 |
| 15 | 146036139347 |
| 16 | 473924014599 |
| 17 | 1494785958435 |
| 18 | 4591920193357 |
| 19 | 13764656869425 |
| 20 | 40328218603134 |