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 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 5 |
| 6 | 19 |
| 7 | 132 |
| 8 | 1579 |
| 9 | 33366 |
| 10 | 1343120 |
| 11 | 105723785 |
| 12 | 15968704512 |
| 13 | 4520384306832 |
| 14 | 2402302590759788 |
| 15 | 2425409960013204929 |
| 16 | 4647586298937784001491 |
| 17 | 16787189663016572148130262 |
| 18 | 114715448859703502223876433517 |