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 | 2 |
| 3 | -7 |
| 4 | 31 |
| 5 | -161 |
| 6 | 976 |
| 7 | -6847 |
| 8 | 54797 |
| 9 | -493201 |
| 10 | 4932046 |
| 11 | -54252551 |
| 12 | 651030667 |
| 13 | -8463398737 |
| 14 | 118487582396 |
| 15 | -1777313736031 |
| 16 | 28437019776601 |
| 17 | -483429336202337 |
| 18 | 8701728051642202 |
| 19 | -165332832981201991 |
| 20 | 3306656659624039991 |