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 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 17 |
| 5 | 85 |
| 6 | 499 |
| 7 | 3422 |
| 8 | 26888 |
| 9 | 238157 |
| 10 | 2347553 |
| 11 | 25487720 |
| 12 | 302211542 |
| 13 | 3885576978 |
| 14 | 53842995267 |
| 15 | 799953072548 |
| 16 | 12684970150410 |
| 17 | 213832353964066 |
| 18 | 3818434892215473 |
| 19 | 72004772253206072 |
| 20 | 1429809049027949159 |