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 | 13 |
| 3 | 55 |
| 4 | 1235 |
| 5 | 4615 |
| 6 | 55801 |
| 7 | 200343 |
| 8 | 8977475 |
| 9 | 36804235 |
| 10 | 367235363 |
| 11 | 1444888289 |
| 12 | 32062742231 |
| 13 | 120729974115 |
| 14 | 1205864254225 |
| 15 | 5201022002071 |
| 16 | 395884671433315 |
| 17 | 1603069490974835 |
| 18 | 15989295873680415 |
| 19 | 64312573140322525 |
| 20 | 1250332447587844829 |
| 21 | 5262481040435242585 |