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 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 60 |
| 6 | 210 |
| 7 | 756 |
| 8 | 2952 |
| 9 | 11565 |
| 10 | 46550 |
| 11 | 187803 |
| 12 | 763200 |
| 13 | 3101683 |
| 14 | 12627594 |
| 15 | 51398640 |
| 16 | 209268080 |
| 17 | 851834453 |
| 18 | 3467196936 |
| 19 | 14109860408 |
| 20 | 57413439000 |
| 21 | 233584274238 |
| 22 | 950220869136 |
| 23 | 3865081177744 |
| 24 | 15719992809672 |
| 25 | 63930676119100 |