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) |
|---|---|
| 4 | 1 |
| 5 | 0 |
| 6 | 15 |
| 7 | 70 |
| 8 | 630 |
| 9 | 5544 |
| 10 | 55650 |
| 11 | 611820 |
| 12 | 7342335 |
| 13 | 95449640 |
| 14 | 1336295961 |
| 15 | 20044438050 |
| 16 | 320711010620 |
| 17 | 5452087178160 |
| 18 | 98137569209940 |
| 19 | 1864613814984984 |
| 20 | 37292276299704525 |
| 21 | 783137802293789040 |
| 22 | 17229031650463366195 |
| 23 | 396267727960657413630 |