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 | -4 |
| 2 | 37 |
| 3 | -232 |
| 4 | 1705 |
| 5 | -11692 |
| 6 | 82573 |
| 7 | -575824 |
| 8 | 4037329 |
| 9 | -28241620 |
| 10 | 197750389 |
| 11 | -1384075576 |
| 12 | 9689060473 |
| 13 | -67821828988 |
| 14 | 474757585885 |
| 15 | -3323288752288 |
| 16 | 23263064312737 |
| 17 | -162841321048996 |
| 18 | 1139889634763461 |
| 19 | -7979226281082760 |
| 20 | 55854587454363721 |
| 21 | -390982101720192844 |