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 | 0 |
| 2 | -1 |
| 3 | -1 |
| 4 | 5 |
| 5 | 19 |
| 6 | -41 |
| 7 | -519 |
| 8 | -183 |
| 9 | 19223 |
| 10 | 73451 |
| 11 | -847067 |
| 12 | -8554547 |
| 13 | 32488611 |
| 14 | 977198559 |
| 15 | 1325135969 |
| 16 | -116987762287 |
| 17 | -860498433233 |
| 18 | 13730866757587 |
| 19 | 243612350234973 |
| 20 | -1120827248102379 |
| 21 | -62079344419449925 |
| 22 | -185852602587850681 |
| 23 | 15185914155303053209 |