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 | 2 |
| 3 | -4 |
| 4 | 10 |
| 5 | -20 |
| 6 | 36 |
| 7 | -72 |
| 8 | 154 |
| 9 | -308 |
| 10 | 596 |
| 11 | -1192 |
| 12 | 2420 |
| 13 | -4840 |
| 14 | 9608 |
| 15 | -19216 |
| 16 | 38586 |
| 17 | -77172 |
| 18 | 154036 |
| 19 | -308072 |
| 20 | 616740 |
| 21 | -1233480 |
| 22 | 2465768 |
| 23 | -4931536 |
| 24 | 9865492 |
| 25 | -19730984 |
| 26 | 39457128 |
| 27 | -78914256 |
| 28 | 157838120 |
| 29 | -315676240 |
| 30 | 631333264 |
| 31 | -1262666528 |
| 32 | 2525371642 |
| 33 | -5050743284 |