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 | 7 |
| 5 | 28 |
| 6 | 124 |
| 7 | 588 |
| 8 | 2938 |
| 9 | 15268 |
| 10 | 81826 |
| 11 | 449572 |
| 12 | 2521270 |
| 13 | 14385376 |
| 14 | 83290424 |
| 15 | 488384528 |
| 16 | 2895432660 |
| 17 | 17332874364 |
| 18 | 104653427012 |
| 19 | 636737003384 |
| 20 | 3900770002646 |
| 21 | 24045500114388 |
| 22 | 149059814328236 |
| 23 | 928782423033008 |
| 24 | 5814401613289290 |
| 25 | 36556766640745936 |