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 | 0 |
| 2 | 2 |
| 3 | 0 |
| 4 | 12 |
| 5 | 0 |
| 6 | 2144 |
| 7 | 0 |
| 8 | 9277152 |
| 9 | 0 |
| 10 | 934520913216 |
| 11 | 0 |
| 12 | 2152453777211211412 |
| 13 | 0 |
| 14 | 112252999240982874562527216 |
| 15 | 0 |
| 16 | 131765033045251672652319572331061144 |
| 17 | 0 |
| 18 | 3467852755777932367855581588111341658695967892 |
| 19 | 0 |