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 | 3 |
| 3 | 18 |
| 4 | 142 |
| 5 | 1350 |
| 6 | 14607 |
| 7 | 174626 |
| 8 | 2263749 |
| 9 | 31426878 |
| 10 | 463144150 |
| 11 | 7199095692 |
| 12 | 117452998632 |
| 13 | 2003613768328 |
| 14 | 35628141598164 |
| 15 | 658723330672311 |
| 16 | 12636278430184303 |
| 17 | 251042922016657782 |
| 18 | 5156985005918404047 |
| 19 | 109382326645948764003 |
| 20 | 2392477607054828471286 |