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 | 3 |
| 1 | 3 |
| 2 | 6 |
| 3 | 56 |
| 4 | 258 |
| 5 | 6264 |
| 6 | 52136 |
| 7 | 1559520 |
| 8 | 17041416 |
| 9 | 706911048 |
| 10 | 10102223208 |
| 11 | 706019328000 |
| 12 | 9101898907920 |
| 13 | 519285252355776 |
| 14 | 11672709747324912 |
| 15 | 880565163670372352 |
| 16 | 18446811354131136516 |
| 17 | 1792353900753729655758 |
| 18 | 54357680125881245248800 |
| 19 | 4154723599066412190910560 |