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 | 5 |
| 4 | 13 |
| 5 | 35 |
| 6 | 96 |
| 7 | 264 |
| 8 | 719 |
| 9 | 1913 |
| 10 | 4875 |
| 11 | 11478 |
| 12 | 22860 |
| 13 | 26044 |
| 14 | -77216 |
| 15 | -793820 |
| 16 | -4394125 |
| 17 | -20304455 |
| 18 | -85805571 |
| 19 | -343282020 |
| 20 | -1321898694 |
| 21 | -4943906064 |
| 22 | -18052305410 |
| 23 | -64551823869 |
| 24 | -226418611750 |
| 25 | -779487689870 |
| 26 | -2633172840764 |
| 27 | -8717790419014 |