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 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 60 |
| 5 | 406 |
| 6 | 3120 |
| 7 | 26823 |
| 8 | 257022 |
| 9 | 2712926 |
| 10 | 31311886 |
| 11 | 392308000 |
| 12 | 5302926524 |
| 13 | 76924127104 |
| 14 | 1191973363059 |
| 15 | 19650226851964 |
| 16 | 343408795841627 |
| 17 | 6341818750193544 |
| 18 | 123405357866753108 |
| 19 | 2523790088462591703 |
| 20 | 54119963305579115810 |
| 21 | 1214292989338825766682 |