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 | -1 |
| 3 | -2 |
| 4 | 5 |
| 5 | 14 |
| 6 | -40 |
| 7 | -119 |
| 8 | 351 |
| 9 | 1083 |
| 10 | -3291 |
| 11 | -10424 |
| 12 | 32562 |
| 13 | 105066 |
| 14 | -334666 |
| 15 | -1094595 |
| 16 | 3536043 |
| 17 | 11686231 |
| 18 | -38172425 |
| 19 | -127199414 |
| 20 | 419230644 |
| 21 | 1406346735 |
| 22 | -4669311299 |
| 23 | -15750517780 |
| 24 | 52616257231 |
| 25 | 178312867791 |
| 26 | -598779740235 |
| 27 | -2037290707630 |
| 28 | 6871904761413 |
| 29 | 23461177498832 |