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 | 21 |
| 4 | 20 |
| 5 | 1555 |
| 6 | 2604 |
| 7 | 299593 |
| 8 | 820 |
| 9 | 29127 |
| 10 | 348678440 |
| 11 | 67546215517 |
| 12 | 20345052 |
| 13 | 61054982558011 |
| 14 | 281241170407092 |
| 15 | 76861433640456465 |
| 16 | 2690420 |
| 17 | 128583032925805678351 |
| 18 | 211927625868 |
| 19 | 275941052631578947368421 |
| 20 | 174339220 |