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) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 21 |
| 6 | 81 |
| 7 | 351 |
| 8 | 1233 |
| 9 | 5769 |
| 10 | 31041 |
| 11 | 142011 |
| 12 | 776601 |
| 13 | 4874013 |
| 14 | 27027729 |
| 15 | 168369111 |
| 16 | 1191911841 |
| 17 | 7678566801 |
| 18 | 53474964993 |
| 19 | 418199988339 |
| 20 | 3044269834281 |
| 21 | 23364756531621 |
| 22 | 199008751634001 |
| 23 | 1605461415071823 |
| 24 | 13428028220072049 |
| 25 | 123280859122040601 |