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 | 2 |
| 5 | -5 |
| 6 | 13 |
| 7 | -40 |
| 8 | 126 |
| 9 | -409 |
| 10 | 1363 |
| 11 | -4617 |
| 12 | 15896 |
| 13 | -55444 |
| 14 | 195480 |
| 15 | -695636 |
| 16 | 2495118 |
| 17 | -9011281 |
| 18 | 32741839 |
| 19 | -119601339 |
| 20 | 438968354 |
| 21 | -1618006837 |
| 22 | 5986803522 |
| 23 | -22229028994 |
| 24 | 82798248894 |
| 25 | -309299225632 |
| 26 | 1158483827048 |
| 27 | -4349740078410 |
| 28 | 16368842606820 |
| 29 | -61727972554068 |
| 30 | 233233590724532 |
| 31 | -882851162632794 |
| 32 | 3347489178793192 |
| 33 | -12712739206990305 |