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 | 1 |
| 3 | 6 |
| 4 | 24 |
| 5 | 320 |
| 6 | 3270 |
| 7 | 55482 |
| 8 | 999656 |
| 9 | 21718440 |
| 10 | 544829130 |
| 11 | 15130478990 |
| 12 | 475440344412 |
| 13 | 16294653237876 |
| 14 | 613546243029902 |
| 15 | 25016884214147490 |
| 16 | 1100408748640263120 |
| 17 | 51948228453097163312 |
| 18 | 2617775548597611727506 |
| 19 | 140364712844785892810646 |
| 20 | 7975414423897012183673540 |