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 | 4 |
| 3 | 25 |
| 4 | 201 |
| 5 | 1773 |
| 6 | 16751 |
| 7 | 165083 |
| 8 | 1681341 |
| 9 | 17562238 |
| 10 | 187255089 |
| 11 | 2030853040 |
| 12 | 22344663465 |
| 13 | 248900855994 |
| 14 | 2802367768848 |
| 15 | 31848644363490 |
| 16 | 364960085991118 |
| 17 | 4212964989100093 |
| 18 | 48953036382441044 |
| 19 | 572178690287957687 |
| 20 | 6723501191850208483 |
| 21 | 79388206896842420091 |