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 | 9 |
| 4 | 66 |
| 5 | 345 |
| 6 | 1590 |
| 7 | 6909 |
| 8 | 29106 |
| 9 | 120465 |
| 10 | 493230 |
| 11 | 2005509 |
| 12 | 8116746 |
| 13 | 32744985 |
| 14 | 131801670 |
| 15 | 529647309 |
| 16 | 2125861986 |
| 17 | 8525167905 |
| 18 | 34165634910 |
| 19 | 136857036309 |
| 20 | 548010848826 |
| 21 | 2193789933225 |
| 22 | 8780396200950 |
| 23 | 35137287916509 |