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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 0 |
| 7 | 1 |
| 8 | 3 |
| 9 | -29 |
| 10 | 25 |
| 11 | 263 |
| 12 | -1481 |
| 13 | -5493 |
| 14 | 80505 |
| 15 | 41549 |
| 16 | -10584341 |
| 17 | 14534299 |
| 18 | 431101045 |
| 19 | -1767586509 |
| 20 | -43076199745 |
| 21 | 322525095431 |
| 22 | 1295531336537 |
| 23 | -30908646610497 |
| 24 | -734222129667169 |
| 25 | 13259294064756895 |
| 26 | 59705027567272273 |
| 27 | -1617292893727823431 |
| 28 | -1346735121534484263 |