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 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 48 |
| 6 | 186 |
| 7 | 712 |
| 8 | 2717 |
| 9 | 10432 |
| 10 | 40222 |
| 11 | 155384 |
| 12 | 601426 |
| 13 | 2332640 |
| 14 | 9063380 |
| 15 | 35269392 |
| 16 | 137438685 |
| 17 | 536257280 |
| 18 | 2094786870 |
| 19 | 8191506136 |
| 20 | 32063203590 |
| 21 | 125613386912 |
| 22 | 492516592620 |
| 23 | 1932569186288 |
| 24 | 7588478653938 |
| 25 | 29816630378368 |
| 26 | 117226929901676 |
| 27 | 461151757861552 |