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 | 1 |
| 2 | 1 |
| 3 | -2 |
| 4 | -23 |
| 5 | -104 |
| 6 | -119 |
| 7 | 3088 |
| 8 | 37297 |
| 9 | 209536 |
| 10 | -569039 |
| 11 | -29795072 |
| 12 | -376722983 |
| 13 | -1715047424 |
| 14 | 35167499641 |
| 15 | 1004215072768 |
| 16 | 12109139111137 |
| 17 | -1945682345984 |
| 18 | -3571363955938079 |
| 19 | -84438462955323392 |
| 20 | -825288198538588343 |
| 21 | 12032890515685113856 |