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 | 9 |
| 3 | 47 |
| 4 | 154 |
| 5 | 274 |
| 6 | 120 |
| 7 | -120 |
| 8 | 240 |
| 9 | -720 |
| 10 | 2880 |
| 11 | -14400 |
| 12 | 86400 |
| 13 | -604800 |
| 14 | 4838400 |
| 15 | -43545600 |
| 16 | 435456000 |
| 17 | -4790016000 |
| 18 | 57480192000 |
| 19 | -747242496000 |
| 20 | 10461394944000 |
| 21 | -156920924160000 |
| 22 | 2510734786560000 |
| 23 | -42682491371520000 |
| 24 | 768284844687360000 |
| 25 | -14597412049059840000 |