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 | 5 |
| 3 | 11 |
| 4 | 6 |
| 5 | -6 |
| 6 | 12 |
| 7 | -36 |
| 8 | 144 |
| 9 | -720 |
| 10 | 4320 |
| 11 | -30240 |
| 12 | 241920 |
| 13 | -2177280 |
| 14 | 21772800 |
| 15 | -239500800 |
| 16 | 2874009600 |
| 17 | -37362124800 |
| 18 | 523069747200 |
| 19 | -7846046208000 |
| 20 | 125536739328000 |
| 21 | -2134124568576000 |
| 22 | 38414242234368000 |
| 23 | -729870602452992000 |
| 24 | 14597412049059840000 |