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 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 18 |
| 4 | 104 |
| 5 | 580 |
| 6 | 3282 |
| 7 | 19236 |
| 8 | 117672 |
| 9 | 753048 |
| 10 | 5041880 |
| 11 | 35283402 |
| 12 | 257718540 |
| 13 | 1961679824 |
| 14 | 15534932350 |
| 15 | 127788932430 |
| 16 | 1090212468512 |
| 17 | 9632275777296 |
| 18 | 88013486026710 |
| 19 | 830637659785996 |
| 20 | 8087069127986020 |
| 21 | 81132805319035260 |
| 22 | 837852685505824120 |
| 23 | 8897619270153977254 |