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 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 36 |
| 5 | 144 |
| 6 | 651 |
| 7 | 3015 |
| 8 | 14634 |
| 9 | 72654 |
| 10 | 369063 |
| 11 | 1904985 |
| 12 | 9971889 |
| 13 | 52788393 |
| 14 | 282161025 |
| 15 | 1520597895 |
| 16 | 8253281871 |
| 17 | 45075359277 |
| 18 | 247534382298 |
| 19 | 1365994896264 |
| 20 | 7571065357620 |
| 21 | 42127865408028 |
| 22 | 235246997219400 |
| 23 | 1317894484506336 |