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 | -3 |
| 3 | -7 |
| 4 | -17 |
| 5 | -45 |
| 6 | -129 |
| 7 | -393 |
| 8 | -1251 |
| 9 | -4111 |
| 10 | -13835 |
| 11 | -47427 |
| 12 | -164999 |
| 13 | -581023 |
| 14 | -2066823 |
| 15 | -7415703 |
| 16 | -26805393 |
| 17 | -97520733 |
| 18 | -356810313 |
| 19 | -1312087713 |
| 20 | -4846614093 |
| 21 | -17974854933 |
| 22 | -66907388973 |
| 23 | -249872516253 |
| 24 | -935991743553 |
| 25 | -3515800038201 |
| 26 | -13239692841105 |