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 | 0 |
| 5 | -6 |
| 6 | -33 |
| 7 | -143 |
| 8 | -572 |
| 9 | -2210 |
| 10 | -8398 |
| 11 | -31654 |
| 12 | -118864 |
| 13 | -445740 |
| 14 | -1671525 |
| 15 | -6273135 |
| 16 | -23571780 |
| 17 | -88704330 |
| 18 | -334347090 |
| 19 | -1262330850 |
| 20 | -4773905760 |
| 21 | -18083762580 |
| 22 | -68611922730 |
| 23 | -260725306374 |
| 24 | -992233959480 |
| 25 | -3781513867796 |
| 26 | -14431491699548 |
| 27 | -55147299002348 |