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 | 3 |
| 3 | 15 |
| 4 | 111 |
| 5 | 1071 |
| 6 | 12663 |
| 7 | 177255 |
| 8 | 2866671 |
| 9 | 52587711 |
| 10 | 1078805223 |
| 11 | 24470577495 |
| 12 | 608113846431 |
| 13 | 16429992037551 |
| 14 | 479502707791383 |
| 15 | 15032820820737735 |
| 16 | 503852219871917391 |
| 17 | 17978716725920562591 |
| 18 | 680458944566818819143 |
| 19 | 27227452811905815729975 |
| 20 | 1148414905826479180087551 |