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 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 26 |
| 5 | 224 |
| 6 | 2244 |
| 7 | 28496 |
| 8 | 417976 |
| 9 | 7122384 |
| 10 | 136770960 |
| 11 | 2937770472 |
| 12 | 69626588976 |
| 13 | 1806936836184 |
| 14 | 50936933449752 |
| 15 | 1550292926398680 |
| 16 | 50661309325357824 |
| 17 | 1769286989373994752 |
| 18 | 65762170385201959680 |
| 19 | 2591979585702305271552 |
| 20 | 107982615297265761991680 |