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 | 4 |
| 3 | 12 |
| 4 | 39 |
| 5 | 129 |
| 6 | 436 |
| 7 | 1498 |
| 8 | 5218 |
| 9 | 18386 |
| 10 | 65420 |
| 11 | 234734 |
| 12 | 848403 |
| 13 | 3086001 |
| 14 | 11288412 |
| 15 | 41499354 |
| 16 | 153247278 |
| 17 | 568188606 |
| 18 | 2114334312 |
| 19 | 7893906144 |
| 20 | 29561195238 |
| 21 | 111007927386 |
| 22 | 417918303144 |
| 23 | 1577061975492 |
| 24 | 5964172347604 |
| 25 | 22601012748124 |
| 26 | 85806694043116 |
| 27 | 326343785428946 |
| 28 | 1243200250005995 |