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 | 2 |
| 5 | 1550 |
| 6 | 546516 |
| 7 | 28482279 |
| 8 | 585632520 |
| 9 | 6829066665 |
| 10 | 54504255500 |
| 11 | 331490619174 |
| 12 | 1642426038486 |
| 13 | 6930083422496 |
| 14 | 25686190415144 |
| 15 | 85541928717375 |
| 16 | 260349711114720 |
| 17 | 733731834393719 |
| 18 | 1934755847570808 |
| 19 | 4813391235753128 |
| 20 | 11375736647373750 |
| 21 | 25684539545337246 |