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) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 44 |
| 5 | 264 |
| 6 | 1020 |
| 7 | 8160 |
| 8 | 19680 |
| 9 | 55104 |
| 10 | 182784 |
| 11 | 2193408 |
| 12 | 4608000 |
| 13 | 64512000 |
| 14 | 210524160 |
| 15 | 560849520 |
| 16 | 964157040 |
| 17 | 17354826720 |
| 18 | 32092508448 |
| 19 | 641850168960 |
| 20 | 1302952210560 |
| 21 | 3134374548480 |
| 22 | 9806680558080 |
| 23 | 235360333393920 |
| 24 | 374108929689600 |
| 25 | 740882390169600 |