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 | 20 |
| 4 | 74 |
| 5 | 276 |
| 6 | 1044 |
| 7 | 3998 |
| 8 | 15450 |
| 9 | 60128 |
| 10 | 235332 |
| 11 | 925332 |
| 12 | 3652508 |
| 13 | 14464490 |
| 14 | 57442074 |
| 15 | 228670140 |
| 16 | 912239782 |
| 17 | 3646027752 |
| 18 | 14596600800 |
| 19 | 58523194734 |
| 20 | 234954663396 |
| 21 | 944418233612 |
| 22 | 3800327339532 |
| 23 | 15307785490560 |
| 24 | 61716607166724 |
| 25 | 249033637247898 |
| 26 | 1005661821858414 |