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 | 4 |
| 3 | 20 |
| 4 | 145 |
| 5 | 1441 |
| 6 | 18248 |
| 7 | 280392 |
| 8 | 5063361 |
| 9 | 105063361 |
| 10 | 2463011052 |
| 11 | 64380375276 |
| 12 | 1856540769313 |
| 13 | 58550453144609 |
| 14 | 2004745521503984 |
| 15 | 74062339559431920 |
| 16 | 2936485391069247713 |
| 17 | 124376016487663499489 |
| 18 | 5604762874272465685428 |