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 | 1 |
| 2 | 5 |
| 3 | 180 |
| 4 | 2640 |
| 5 | 23100 |
| 6 | 157080 |
| 7 | 183260 |
| 8 | 2408560 |
| 9 | 317026710 |
| 10 | 10215305100 |
| 11 | 89894684880 |
| 12 | 19613385792 |
| 13 | 403708857552 |
| 14 | 17825298787296 |
| 15 | 8681152006800 |
| 16 | 435215087274240 |
| 17 | 2312080151144400 |
| 18 | 43249499297877600 |
| 19 | 45652249258870800 |
| 20 | 2835244953971976000 |
| 21 | 4394629678656562800 |