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 | 0 |
| 2 | -3 |
| 3 | -15 |
| 4 | -63 |
| 5 | -252 |
| 6 | -990 |
| 7 | -3861 |
| 8 | -15012 |
| 9 | -58293 |
| 10 | -226233 |
| 11 | -877797 |
| 12 | -3405564 |
| 13 | -13211910 |
| 14 | -51254775 |
| 15 | -198838152 |
| 16 | -771371667 |
| 17 | -2992450959 |
| 18 | -11608875207 |
| 19 | -45035307612 |
| 20 | -174709321686 |
| 21 | -677764787229 |
| 22 | -2629310751036 |
| 23 | -10200109386213 |
| 24 | -39570153919641 |
| 25 | -153507871295037 |