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 | 2 |
| 2 | -4 |
| 3 | -9 |
| 4 | 19 |
| 5 | 43 |
| 6 | -91 |
| 7 | -206 |
| 8 | 436 |
| 9 | 987 |
| 10 | -2089 |
| 11 | -4729 |
| 12 | 10009 |
| 13 | 22658 |
| 14 | -47956 |
| 15 | -108561 |
| 16 | 229771 |
| 17 | 520147 |
| 18 | -1100899 |
| 19 | -2492174 |
| 20 | 5274724 |
| 21 | 11940723 |
| 22 | -25272721 |
| 23 | -57211441 |
| 24 | 121088881 |
| 25 | 274116482 |
| 26 | -580171684 |
| 27 | -1313370969 |
| 28 | 2779769539 |
| 29 | 6292738363 |
| 30 | -13318676011 |