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 | 0 |
| 3 | 1 |
| 4 | 11 |
| 5 | 39 |
| 6 | 473 |
| 7 | 19897 |
| 8 | 63683 |
| 9 | 5731597 |
| 10 | 22926439 |
| 11 | 280212089 |
| 12 | 20175270749 |
| 13 | 224810160067 |
| 14 | 6294684482461 |
| 15 | 1321883741325001 |
| 16 | 1208579420640469 |
| 17 | 68486167169628137 |
| 18 | 17258514126746312369 |
| 19 | 178860964586279976467 |
| 20 | 6053755724458706915971 |
| 21 | 3305350625554453976644453 |