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 | 4 |
| 2 | 15 |
| 3 | 55 |
| 4 | 201 |
| 5 | 739 |
| 6 | 2745 |
| 7 | 10315 |
| 8 | 39201 |
| 9 | 150499 |
| 10 | 582825 |
| 11 | 2273275 |
| 12 | 8918001 |
| 13 | 35144659 |
| 14 | 138992505 |
| 15 | 551203435 |
| 16 | 2190497601 |
| 17 | 8719009219 |
| 18 | 34747027785 |
| 19 | 138600952795 |
| 20 | 553242074001 |
| 21 | 2209482560179 |
| 22 | 8827471984665 |
| 23 | 35278511073355 |