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 | 2 |
| 2 | -1 |
| 3 | 3 |
| 4 | -12 |
| 5 | 59 |
| 6 | -354 |
| 7 | 2535 |
| 8 | -21190 |
| 9 | 202731 |
| 10 | -2183462 |
| 11 | 26130441 |
| 12 | -343956264 |
| 13 | 4938891841 |
| 14 | -76827253854 |
| 15 | 1287026203647 |
| 16 | -23100628140676 |
| 17 | 442271719973507 |
| 18 | -8996704216880580 |
| 19 | 193776558133638811 |
| 20 | -4405549734148088108 |
| 21 | 105432710994387193283 |
| 22 | -2649353692976978990070 |