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 | 2 |
| 4 | 4 |
| 5 | 18 |
| 6 | 42 |
| 7 | 156 |
| 8 | 398 |
| 9 | 1398 |
| 10 | 3778 |
| 11 | 12982 |
| 12 | 36522 |
| 13 | 124290 |
| 14 | 360182 |
| 15 | 1220440 |
| 16 | 3618090 |
| 17 | 12237698 |
| 18 | 36938158 |
| 19 | 124880222 |
| 20 | 382471606 |
| 21 | 1293363816 |
| 22 | 4009185912 |
| 23 | 13565790984 |
| 24 | 42478788432 |
| 25 | 143851766298 |
| 26 | 454339269482 |
| 27 | 1539997455570 |
| 28 | 4900091676662 |
| 29 | 16624834778474 |
| 30 | 53240459608298 |