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 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 15 |
| 7 | 140 |
| 8 | 1050 |
| 9 | 6951 |
| 10 | 42524 |
| 11 | 246730 |
| 12 | 1379385 |
| 13 | 7508501 |
| 14 | 40074895 |
| 15 | 210766919 |
| 16 | 1096189500 |
| 17 | 5652751651 |
| 18 | 28958088579 |
| 19 | 147589284710 |
| 20 | 749206047975 |
| 21 | 3791262568261 |
| 22 | 19137821665325 |
| 23 | 96416888184100 |