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 | 1 |
| 3 | 3 |
| 4 | 14 |
| 5 | 80 |
| 6 | 518 |
| 7 | 3647 |
| 8 | 27274 |
| 9 | 213480 |
| 10 | 1731652 |
| 11 | 14455408 |
| 12 | 123552488 |
| 13 | 1077096124 |
| 14 | 9548805240 |
| 15 | 85884971043 |
| 16 | 782242251522 |
| 17 | 7203683481720 |
| 18 | 66989439309452 |
| 19 | 628399635777936 |
| 20 | 5940930064989720 |
| 21 | 56562734108608536 |