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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5034 |
| 8 | 40087 |
| 9 | 356942 |
| 10 | 3500551 |
| 11 | 37343168 |
| 12 | 428886219 |
| 13 | 5257753614 |
| 14 | 68306562647 |
| 15 | 934747457369 |
| 16 | 13404687958473 |
| 17 | 200554264435218 |
| 18 | 3118638648191005 |
| 19 | 50236367074036768 |
| 20 | 835860362285064716 |