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 | 2 |
| 2 | 9 |
| 3 | 58 |
| 4 | 401 |
| 5 | 2802 |
| 6 | 19609 |
| 7 | 137258 |
| 8 | 960801 |
| 9 | 6725602 |
| 10 | 47079209 |
| 11 | 329554458 |
| 12 | 2306881201 |
| 13 | 16148168402 |
| 14 | 113037178809 |
| 15 | 791260251658 |
| 16 | 5538821761601 |
| 17 | 38771752331202 |
| 18 | 271402266318409 |
| 19 | 1899815864228858 |
| 20 | 13298711049602001 |
| 21 | 93090977347214002 |
| 22 | 651636841430498009 |
| 23 | 4561457890013486058 |