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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 0 |
| 5 | 1 |
| 6 | -7 |
| 7 | 1 |
| 8 | 53 |
| 9 | -281 |
| 10 | -1231 |
| 11 | 87379 |
| 12 | -13303471 |
| 13 | -54313201 |
| 14 | 10142361989 |
| 15 | 2821265977 |
| 16 | -10502027401553 |
| 17 | 1836446156249 |
| 18 | 2952828271088741 |
| 19 | -1004826382596003137 |
| 20 | -7006246797736924249 |
| 21 | 14607119841651449406947 |
| 22 | 1868869263315549659372569 |