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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 6 |
| 6 | 13 |
| 7 | 36 |
| 8 | 93 |
| 9 | 243 |
| 10 | 645 |
| 11 | 1782 |
| 12 | 4914 |
| 13 | 13608 |
| 14 | 37890 |
| 15 | 106288 |
| 16 | 299025 |
| 17 | 844182 |
| 18 | 2391363 |
| 19 | 6797196 |
| 20 | 19371684 |
| 21 | 55345784 |
| 22 | 158486625 |
| 23 | 454795398 |
| 24 | 1307541690 |
| 25 | 3765720066 |
| 26 | 10862647236 |
| 27 | 31381059609 |
| 28 | 90780960426 |
| 29 | 262951692390 |