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 | 2 |
| 3 | 4 |
| 4 | 6 |
| 5 | -4 |
| 6 | -100 |
| 7 | -664 |
| 8 | -3514 |
| 9 | -16916 |
| 10 | -77388 |
| 11 | -343144 |
| 12 | -1490148 |
| 13 | -6376616 |
| 14 | -26992264 |
| 15 | -113317936 |
| 16 | -472661434 |
| 17 | -1961361076 |
| 18 | -8104733884 |
| 19 | -33374212936 |
| 20 | -137031378124 |
| 21 | -561253753336 |
| 22 | -2293947547384 |
| 23 | -9358755316816 |
| 24 | -38121140494564 |
| 25 | -155064370272904 |