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 | 5 |
| 3 | 15 |
| 4 | 45 |
| 5 | 132 |
| 6 | 381 |
| 7 | 1086 |
| 8 | 3060 |
| 9 | 8531 |
| 10 | 23563 |
| 11 | 64560 |
| 12 | 175639 |
| 13 | 474790 |
| 14 | 1275929 |
| 15 | 3410180 |
| 16 | 9068075 |
| 17 | 23998671 |
| 18 | 63230680 |
| 19 | 165904474 |
| 20 | 433596795 |
| 21 | 1129037237 |
| 22 | 2929620046 |
| 23 | 7576584801 |
| 24 | 19532878559 |
| 25 | 50205938903 |
| 26 | 128676829149 |
| 27 | 328895341731 |
| 28 | 838453003422 |