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 | 5 |
| 3 | 19 |
| 4 | 145 |
| 5 | 601 |
| 6 | 8521 |
| 7 | 35281 |
| 8 | 672001 |
| 9 | 4898881 |
| 10 | 82615681 |
| 11 | 439084801 |
| 12 | 21138606721 |
| 13 | 80951270401 |
| 14 | 3358578263041 |
| 15 | 49506372115201 |
| 16 | 1227603183206401 |
| 17 | 6046686277632001 |
| 18 | 611515751899852801 |
| 19 | 2311256907767808001 |
| 20 | 254421414038266675201 |
| 21 | 4015778465971464192001 |