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 | -7 |
| 2 | 41 |
| 3 | -253 |
| 4 | 1555 |
| 5 | -9532 |
| 6 | 58463 |
| 7 | -358600 |
| 8 | 2199546 |
| 9 | -13491360 |
| 10 | 82752059 |
| 11 | -507576937 |
| 12 | 3113328401 |
| 13 | -19096245457 |
| 14 | 117130782240 |
| 15 | -718445946527 |
| 16 | 4406737223117 |
| 17 | -27029636742811 |
| 18 | 165791883077354 |
| 19 | -1016918901125280 |
| 20 | 6237482995373629 |
| 21 | -38258895644996020 |