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 | 6 |
| 3 | 51 |
| 4 | 462 |
| 5 | 3809 |
| 6 | 26394 |
| 7 | 150777 |
| 8 | 721382 |
| 9 | 2964632 |
| 10 | 10720688 |
| 11 | 34811491 |
| 12 | 103179440 |
| 13 | 282848319 |
| 14 | 724794396 |
| 15 | 1751160378 |
| 16 | 4017593748 |
| 17 | 8804203831 |
| 18 | 18519925138 |
| 19 | 37551252015 |
| 20 | 73653037370 |
| 21 | 140173677721 |
| 22 | 259538952486 |
| 23 | 468599962315 |