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 | 0 |
| 4 | 5 |
| 5 | -16 |
| 6 | 14 |
| 7 | 96 |
| 8 | -495 |
| 9 | 880 |
| 10 | 2002 |
| 11 | -17888 |
| 12 | 48178 |
| 13 | 19040 |
| 14 | -665380 |
| 15 | 2501312 |
| 16 | -1983543 |
| 17 | -23639952 |
| 18 | 124654250 |
| 19 | -216770400 |
| 20 | -722621130 |
| 21 | 5941209120 |
| 22 | -15657865020 |
| 23 | -12958545600 |
| 24 | 267306817050 |
| 25 | -972419359392 |
| 26 | 534946077108 |
| 27 | 11045425672512 |