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 | 46089 |
| 10 | 434241 |
| 11 | 2359611 |
| 12 | 27387801 |
| 13 | 264333213 |
| 14 | 1722161169 |
| 15 | 16514298711 |
| 16 | 163094452641 |
| 17 | 1216239520401 |
| 18 | 50883607918593 |
| 19 | 866931703203699 |
| 20 | 8473720481213481 |
| 21 | 166915156382509221 |
| 22 | 2699805625227141201 |
| 23 | 28818706120636531023 |
| 24 | 439756550972215638129 |
| 25 | 6766483260087819272601 |
| 26 | 77096822666547068590401 |
| 27 | 3568144263578808757678251 |