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) |
|---|---|
| 3 | -2 |
| 4 | 3 |
| 5 | 0 |
| 6 | 25 |
| 7 | 152 |
| 8 | 1350 |
| 9 | 12644 |
| 10 | 131391 |
| 11 | 1489568 |
| 12 | 18329481 |
| 13 | 243365514 |
| 14 | 3468969962 |
| 15 | 52848096274 |
| 16 | 857073295427 |
| 17 | 14744289690560 |
| 18 | 268202790690465 |
| 19 | 5143861702523924 |
| 20 | 103746422699053582 |
| 21 | 2195275169113687656 |
| 22 | 48629604864202585247 |