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 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 63 |
| 5 | 279 |
| 6 | 1215 |
| 7 | 5319 |
| 8 | 23247 |
| 9 | 101655 |
| 10 | 444447 |
| 11 | 1943271 |
| 12 | 8496495 |
| 13 | 37149111 |
| 14 | 162426303 |
| 15 | 710173575 |
| 16 | 3105078543 |
| 17 | 13576277079 |
| 18 | 59359302495 |
| 19 | 259535569959 |
| 20 | 1134762524847 |
| 21 | 4961500994295 |
| 22 | 21693078131967 |
| 23 | 94848240361671 |
| 24 | 414703189876815 |
| 25 | 1813199011800471 |