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 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 14 |
| 5 | 86 |
| 6 | 566 |
| 7 | 4166 |
| 8 | 34406 |
| 9 | 316646 |
| 10 | 3219686 |
| 11 | 35878886 |
| 12 | 435046886 |
| 13 | 5704064486 |
| 14 | 80428314086 |
| 15 | 1213746099686 |
| 16 | 19521187251686 |
| 17 | 333363035571686 |
| 18 | 6024361885107686 |
| 19 | 114864714882483686 |
| 20 | 2304476522241459686 |