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 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 4 |
| 5 | 15 |
| 6 | -34 |
| 7 | 322 |
| 8 | -2456 |
| 9 | 22269 |
| 10 | -222470 |
| 11 | 2447456 |
| 12 | -29369108 |
| 13 | 381798859 |
| 14 | -5345183466 |
| 15 | 80177752670 |
| 16 | -1282844041904 |
| 17 | 21808348713337 |
| 18 | -392550276838926 |
| 19 | 7458455259940924 |
| 20 | -149169105198816940 |
| 21 | 3132551209175157511 |
| 22 | -68916126601853463218 |