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 | 3 |
| 3 | -3 |
| 4 | 3 |
| 5 | 15 |
| 6 | -57 |
| 7 | 21 |
| 8 | 867 |
| 9 | -1893 |
| 10 | 1581 |
| 11 | 8283 |
| 12 | -76953 |
| 13 | 34203 |
| 14 | 361551 |
| 15 | -869691 |
| 16 | 6420387 |
| 17 | 34130067 |
| 18 | -167946159 |
| 19 | 79445631 |
| 20 | 1696170093 |
| 21 | -4239570255 |
| 22 | 4083041217 |
| 23 | 21859150803 |
| 24 | -442212416121 |
| 25 | 215805655695 |
| 26 | 2316081934929 |
| 27 | -5909439428697 |
| 28 | 11656013746863 |
| 29 | 62663656767603 |
| 30 | -322045194694305 |
| 31 | 160129270032933 |
| 32 | 27589357112530467 |