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 | 1 |
| 3 | 0 |
| 4 | -5 |
| 5 | -24 |
| 6 | -90 |
| 7 | -312 |
| 8 | -1053 |
| 9 | -3536 |
| 10 | -11934 |
| 11 | -40664 |
| 12 | -140114 |
| 13 | -488240 |
| 14 | -1719380 |
| 15 | -6113200 |
| 16 | -21921245 |
| 17 | -79200160 |
| 18 | -288045110 |
| 19 | -1053728920 |
| 20 | -3874721030 |
| 21 | -14313562480 |
| 22 | -53093391980 |
| 23 | -197669347600 |
| 24 | -738398308850 |
| 25 | -2766700765024 |