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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 21 |
| 5 | 134 |
| 6 | 968 |
| 7 | 7662 |
| 8 | 65135 |
| 9 | 587040 |
| 10 | 5559342 |
| 11 | 54965230 |
| 12 | 564651110 |
| 13 | 6004908296 |
| 14 | 65920345700 |
| 15 | 745289233564 |
| 16 | 8661959227407 |
| 17 | 103330815828292 |
| 18 | 1263608418272768 |
| 19 | 15823268263301680 |
| 20 | 202712359166886406 |
| 21 | 2654710188935753950 |
| 22 | 35514167158635839770 |