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 | 4 |
| 2 | 30 |
| 3 | 276 |
| 4 | 2825 |
| 5 | 30884 |
| 6 | 353108 |
| 7 | 4170500 |
| 8 | 50485764 |
| 9 | 623084056 |
| 10 | 7810707894 |
| 11 | 99175174284 |
| 12 | 1272856327470 |
| 13 | 16486135484248 |
| 14 | 215212582153840 |
| 15 | 2828658852385572 |
| 16 | 37401956484705132 |
| 17 | 497174193516767600 |
| 18 | 6640063367021736728 |
| 19 | 89058042321373540912 |
| 20 | 1199031374607501831273 |