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 | 6 |
| 3 | -15 |
| 4 | 90 |
| 5 | -310 |
| 6 | 1860 |
| 7 | -7455 |
| 8 | 44730 |
| 9 | -195426 |
| 10 | 1172556 |
| 11 | -5416026 |
| 12 | 32496156 |
| 13 | -156061620 |
| 14 | 936369720 |
| 15 | -4628393055 |
| 16 | 27770358330 |
| 17 | -140348412490 |
| 18 | 842090474940 |
| 19 | -4331544836190 |
| 20 | 25989269017140 |
| 21 | -135614951248140 |
| 22 | 813689707488840 |
| 23 | -4296741195214650 |
| 24 | 25780447171287900 |