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 | 9 |
| 3 | 60 |
| 4 | 357 |
| 5 | 2088 |
| 6 | 12177 |
| 7 | 70980 |
| 8 | 413709 |
| 9 | 2411280 |
| 10 | 14053977 |
| 11 | 81912588 |
| 12 | 477421557 |
| 13 | 2782616760 |
| 14 | 16218279009 |
| 15 | 94527057300 |
| 16 | 550944064797 |
| 17 | 3211137331488 |
| 18 | 18715879924137 |
| 19 | 109084142213340 |
| 20 | 635788973355909 |
| 21 | 3705649697922120 |
| 22 | 21598109214176817 |
| 23 | 125883005587138788 |