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 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 48 |
| 5 | 10 |
| 6 | -1440 |
| 7 | -17654 |
| 8 | -153216 |
| 9 | -1003950 |
| 10 | -2787840 |
| 11 | 58057538 |
| 12 | 1483941888 |
| 13 | 22381115354 |
| 14 | 245730121728 |
| 15 | 1455189928890 |
| 16 | -18135147970560 |
| 17 | -856283065534046 |
| 18 | -19218870434267136 |
| 19 | -306007541260257422 |
| 20 | -2933654664287354880 |
| 21 | 20552099782407258282 |
| 22 | 1938717354581701951488 |