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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 78 |
| 6 | 230 |
| 7 | 675 |
| 8 | 2069 |
| 9 | 6404 |
| 10 | 19708 |
| 11 | 60216 |
| 12 | 183988 |
| 13 | 563172 |
| 14 | 1725349 |
| 15 | 5284109 |
| 16 | 16177694 |
| 17 | 49526506 |
| 18 | 151635752 |
| 19 | 464286962 |
| 20 | 1421566698 |
| 21 | 4352505527 |
| 22 | 13326304313 |
| 23 | 40802053896 |
| 24 | 124926806216 |
| 25 | 382497958000 |
| 26 | 1171122069784 |
| 27 | 3585709284968 |
| 28 | 10978628154457 |