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) |
|---|---|
| 2 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 47 |
| 6 | 291 |
| 7 | 2084 |
| 8 | 16963 |
| 9 | 154751 |
| 10 | 1564473 |
| 11 | 17363954 |
| 12 | 209931921 |
| 13 | 2746478927 |
| 14 | 38660636899 |
| 15 | 582656032412 |
| 16 | 9361157155491 |
| 17 | 159722327675759 |
| 18 | 2884363055319153 |
| 19 | 54962620378739666 |
| 20 | 1102136770630112473 |
| 21 | 23199834803611101599 |