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 | 0 |
| 1 | -3 |
| 2 | 6 |
| 3 | -9 |
| 4 | 21 |
| 5 | -33 |
| 6 | 72 |
| 7 | -120 |
| 8 | 249 |
| 9 | -432 |
| 10 | 867 |
| 11 | -1545 |
| 12 | 3033 |
| 13 | -5502 |
| 14 | 10644 |
| 15 | -19539 |
| 16 | 37434 |
| 17 | -69261 |
| 18 | 131841 |
| 19 | -245217 |
| 20 | 464784 |
| 21 | -867492 |
| 22 | 1639569 |
| 23 | -3067260 |
| 24 | 5786199 |
| 25 | -10841349 |
| 26 | 20425857 |
| 27 | -38310246 |
| 28 | 72118920 |
| 29 | -135356595 |
| 30 | 254667006 |
| 31 | -478188705 |
| 32 | 899357613 |