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 | -7 |
| 4 | 24 |
| 5 | -75 |
| 6 | 285 |
| 7 | -1036 |
| 8 | 4242 |
| 9 | -16926 |
| 10 | 73206 |
| 11 | -311256 |
| 12 | 1403028 |
| 13 | -6247527 |
| 14 | 29082339 |
| 15 | -134138290 |
| 16 | 640672890 |
| 17 | -3038045010 |
| 18 | 14818136190 |
| 19 | -71858704710 |
| 20 | 356665411440 |
| 21 | -1761879027090 |
| 22 | 8874875097270 |
| 23 | -44526516209280 |
| 24 | 227135946200940 |
| 25 | -1154738374364100 |
| 26 | 5955171596514900 |