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 | 3 |
| 3 | 24 |
| 4 | 229 |
| 5 | 2449 |
| 6 | 28035 |
| 7 | 336100 |
| 8 | 4165920 |
| 9 | 52953884 |
| 10 | 686517601 |
| 11 | 9042628374 |
| 12 | 120669757468 |
| 13 | 1627932844657 |
| 14 | 22166277534398 |
| 15 | 304230231637560 |
| 16 | 4204474770868230 |
| 17 | 58458984141770754 |
| 18 | 817176088436608178 |
| 19 | 11477568712206346244 |
| 20 | 161897000202383717334 |
| 21 | 2292445680627209103645 |