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 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 64 |
| 5 | 230 |
| 6 | 936 |
| 7 | 3822 |
| 8 | 17344 |
| 9 | 78354 |
| 10 | 389280 |
| 11 | 1913010 |
| 12 | 10267776 |
| 13 | 54235350 |
| 14 | 311348352 |
| 15 | 1751907150 |
| 16 | 10673326080 |
| 17 | 63531238050 |
| 18 | 408231498240 |
| 19 | 2556121021650 |
| 20 | 17236028160000 |
| 21 | 113006008398150 |
| 22 | 796296326031360 |
| 23 | 5445783239554350 |
| 24 | 39959419088977920 |
| 25 | 284127133728611250 |