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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | -1 |
| 4 | 0 |
| 5 | 1 |
| 6 | -1 |
| 7 | -4 |
| 8 | 4 |
| 9 | 0 |
| 10 | 0 |
| 11 | 0 |
| 12 | 0 |
| 13 | 0 |
| 14 | 0 |
| 15 | 0 |
| 16 | 4 |
| 17 | 4 |
| 18 | -9 |
| 19 | -25 |
| 20 | 121 |
| 21 | 64 |
| 22 | -576 |
| 23 | -2304 |
| 24 | 3600 |
| 25 | 3136 |
| 26 | -256 |
| 27 | -144 |
| 28 | 961 |
| 29 | 24025 |
| 30 | -47089 |
| 31 | -345744 |
| 32 | 1317904 |
| 33 | 107584 |
| 34 | -26896 |
| 35 | -30976 |
| 36 | 17424 |
| 37 | 30976 |
| 38 | -156025 |
| 39 | -76729 |
| 40 | 485809 |
| 41 | 478864 |
| 42 | -36481 |
| 43 | -837225 |
| 44 | 5776 |
| 45 | 517198564 |
| 46 | -15791440896 |
| 47 | -16404230241 |
| 48 | 45746793225 |