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 | 3 |
| 2 | 9 |
| 3 | 75 |
| 4 | 465 |
| 5 | 7827 |
| 6 | 54489 |
| 7 | 1985883 |
| 8 | 5684385 |
| 9 | 1038408483 |
| 10 | -8440926039 |
| 11 | 1026884514411 |
| 12 | -24803157926799 |
| 13 | 1735078791616947 |
| 14 | -69866656826056839 |
| 15 | 4467425545047012219 |
| 16 | -239734355869361550015 |
| 17 | 15985164846462976491075 |
| 18 | -1031464442408734822175415 |