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 | 0 |
| 3 | 3 |
| 4 | 18 |
| 5 | 90 |
| 6 | 390 |
| 7 | 2205 |
| 8 | 10878 |
| 9 | 45318 |
| 10 | 256350 |
| 11 | 5530305 |
| 12 | 55869330 |
| 13 | 865551258 |
| 14 | 9892489698 |
| 15 | 78223384785 |
| 16 | 470010394350 |
| 17 | 24530527675230 |
| 18 | 409760923017198 |
| 19 | 10595007772540113 |
| 20 | 160826214447439770 |
| 21 | 1585844008081570650 |
| 22 | 16787211082925012730 |
| 23 | 1362379219330719093273 |