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 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | -9 |
| 7 | 70 |
| 8 | -335 |
| 9 | 504 |
| 10 | 11935 |
| 11 | -182094 |
| 12 | 1525833 |
| 13 | -4911764 |
| 14 | -99495473 |
| 15 | 2430329070 |
| 16 | -29988416159 |
| 17 | 158542630224 |
| 18 | 2868272912511 |
| 19 | -102775471991126 |
| 20 | 1714422613948345 |
| 21 | -13166449628575404 |
| 22 | -209400601689898289 |
| 23 | 10598981162761786950 |
| 24 | -227206614609529433199 |