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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 53 |
| 5 | 204 |
| 6 | 3005 |
| 7 | 16006 |
| 8 | 179257 |
| 9 | 1142808 |
| 10 | 11069209 |
| 11 | 78136010 |
| 12 | 698663261 |
| 13 | 5225991012 |
| 14 | 44686481813 |
| 15 | 345446523214 |
| 16 | 2880530655265 |
| 17 | 22687940948016 |
| 18 | 186521884004017 |
| 19 | 1484752874460818 |
| 20 | 12109078065118469 |
| 21 | 96971046978817020 |