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 | 9 |
| 2 | 69 |
| 3 | 502 |
| 4 | 3564 |
| 5 | 24960 |
| 6 | 173325 |
| 7 | 1196748 |
| 8 | 8229849 |
| 9 | 56427177 |
| 10 | 386011116 |
| 11 | 2635972920 |
| 12 | 17974898872 |
| 13 | 122430895956 |
| 14 | 833108684637 |
| 15 | 5664553564440 |
| 16 | 38488954887171 |
| 17 | 261369752763963 |
| 18 | 1774016418598269 |
| 19 | 12035694958994142 |
| 20 | 81624256468292016 |
| 21 | 553377268856455968 |