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 | 2 |
| 3 | 2676 |
| 4 | 101118 |
| 5 | 1644784 |
| 6 | 16044996 |
| 7 | 110148864 |
| 8 | 584716268 |
| 9 | 2549726784 |
| 10 | 9515920164 |
| 11 | 31314134428 |
| 12 | 92917720104 |
| 13 | 252775518960 |
| 14 | 638328487880 |
| 15 | 1511740834560 |
| 16 | 3387163064214 |
| 17 | 7228599229760 |
| 18 | 14768913424614 |
| 19 | 29023937463900 |
| 20 | 55107648867544 |
| 21 | 101434033397472 |