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 | 1 |
| 3 | 3 |
| 4 | 11 |
| 5 | 41 |
| 6 | 151 |
| 7 | 549 |
| 8 | 1977 |
| 9 | 7075 |
| 10 | 25229 |
| 11 | 89831 |
| 12 | 319881 |
| 13 | 1140523 |
| 14 | 4075321 |
| 15 | 14603243 |
| 16 | 52501659 |
| 17 | 189440937 |
| 18 | 686181711 |
| 19 | 2495243373 |
| 20 | 9109701699 |
| 21 | 33388293177 |
| 22 | 122840931891 |
| 23 | 453622854873 |
| 24 | 1681057537359 |
| 25 | 6250742452125 |
| 26 | 23316503569983 |
| 27 | 87236431248445 |