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 | -1 |
| 4 | -13 |
| 5 | -67 |
| 6 | -285 |
| 7 | -1119 |
| 8 | -4215 |
| 9 | -15505 |
| 10 | -56239 |
| 11 | -202309 |
| 12 | -724499 |
| 13 | -2589521 |
| 14 | -9254363 |
| 15 | -33111969 |
| 16 | -118725597 |
| 17 | -426892131 |
| 18 | -1539965973 |
| 19 | -5575175319 |
| 20 | -20260052337 |
| 21 | -73908397851 |
| 22 | -270657727593 |
| 23 | -994938310059 |