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 | 4 |
| 4 | -10 |
| 5 | -92 |
| 6 | 212 |
| 7 | 4744 |
| 8 | -10330 |
| 9 | -440492 |
| 10 | 926972 |
| 11 | 64905784 |
| 12 | -133989700 |
| 13 | -13958115992 |
| 14 | 28507072232 |
| 15 | 4129849252624 |
| 16 | -8382195909370 |
| 17 | -1609609189734092 |
| 18 | 3254514296768492 |
| 19 | 799400112196210264 |
| 20 | -1612314122867559340 |