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 | 3 |
| 2 | 11 |
| 3 | 39 |
| 4 | 139 |
| 5 | 503 |
| 6 | 1847 |
| 7 | 6863 |
| 8 | 25739 |
| 9 | 97239 |
| 10 | 369511 |
| 11 | 1410863 |
| 12 | 5408311 |
| 13 | 20801199 |
| 14 | 80233199 |
| 15 | 310235039 |
| 16 | 1202160779 |
| 17 | 4667212439 |
| 18 | 18150270599 |
| 19 | 70690527599 |
| 20 | 275693057639 |
| 21 | 1076515748879 |
| 22 | 4208197927439 |
| 23 | 16466861455199 |
| 24 | 64495207366199 |
| 25 | 252821212875503 |