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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | -2 |
| 4 | 8 |
| 5 | -40 |
| 6 | 210 |
| 7 | -1032 |
| 8 | 4074 |
| 9 | -9084 |
| 10 | -1485 |
| 11 | -139344 |
| 12 | -1178057 |
| 13 | 97107644 |
| 14 | 533077818 |
| 15 | -43465435335 |
| 16 | -997494915376 |
| 17 | 35039558716800 |
| 18 | 1885975569825115 |
| 19 | -36684866143759995 |
| 20 | -4946226556607087316 |
| 21 | 24828007395162323458 |
| 22 | 18213320246807011794109 |