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 | 0 |
| 2 | 61 |
| 3 | 497 |
| 4 | 902 |
| 5 | 3683 |
| 6 | 23909 |
| 7 | 128242 |
| 8 | 465323 |
| 9 | 1918153 |
| 10 | 10153650 |
| 11 | 48825739 |
| 12 | 206962001 |
| 13 | 913773720 |
| 14 | 4366054069 |
| 15 | 20367538805 |
| 16 | 90798363146 |
| 17 | 409867362675 |
| 18 | 1900191504221 |
| 19 | 8749921654714 |
| 20 | 39674026618581 |
| 21 | 180520404483627 |