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 | -4 |
| 1 | 0 |
| 2 | 20 |
| 3 | 120 |
| 4 | 620 |
| 5 | 3120 |
| 6 | 15620 |
| 7 | 78120 |
| 8 | 390620 |
| 9 | 1953120 |
| 10 | 9765620 |
| 11 | 48828120 |
| 12 | 244140620 |
| 13 | 1220703120 |
| 14 | 6103515620 |
| 15 | 30517578120 |
| 16 | 152587890620 |
| 17 | 762939453120 |
| 18 | 3814697265620 |
| 19 | 19073486328120 |
| 20 | 95367431640620 |
| 21 | 476837158203120 |
| 22 | 2384185791015620 |
| 23 | 11920928955078120 |