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 | -13 |
| 2 | 241 |
| 3 | -234 |
| 4 | 7651 |
| 5 | -6474 |
| 6 | 1294777 |
| 7 | -141414 |
| 8 | 3908371 |
| 9 | -3037554 |
| 10 | 880109741 |
| 11 | -51516894 |
| 12 | 126988371481 |
| 13 | -1698403434 |
| 14 | 41385427951 |
| 15 | 60701726826 |
| 16 | -25346319396013 |
| 17 | -14288276454114 |
| 18 | 52943839266052243 |
| 19 | 3008865450973746 |
| 20 | -1027344973517969959 |
| 21 | -802113321418821594 |