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 | 126 |
| 2 | 5292 |
| 3 | 116424 |
| 4 | 1646568 |
| 5 | 16818516 |
| 6 | 133613766 |
| 7 | 868489479 |
| 8 | 4789851066 |
| 9 | 23029990984 |
| 10 | 98561919456 |
| 11 | 381644355456 |
| 12 | 1354627767168 |
| 13 | 4454641311264 |
| 14 | 13691471089032 |
| 15 | 39620253756006 |
| 16 | 108618373687131 |
| 17 | 283595960194470 |
| 18 | 708397594804900 |
| 19 | 1699573176873000 |