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 | 2 |
| 3 | -10 |
| 4 | -10 |
| 5 | 242 |
| 6 | -678 |
| 7 | -7054 |
| 8 | 88342 |
| 9 | -207646 |
| 10 | -6015904 |
| 11 | 88310862 |
| 12 | -312514816 |
| 13 | -8847633338 |
| 14 | 184252541514 |
| 15 | -1269592841970 |
| 16 | -17662739133178 |
| 17 | 634109114537218 |
| 18 | -7914500471718552 |
| 19 | -18165019012117450 |
| 20 | 2936604063787679650 |
| 21 | -62899139815867627378 |