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 | 2 |
| 2 | 40 |
| 3 | 2436 |
| 4 | 19992 |
| 5 | 231414 |
| 6 | 1152576 |
| 7 | 6272072 |
| 8 | 22219408 |
| 9 | 79002090 |
| 10 | 220032120 |
| 11 | 600454092 |
| 12 | 1407554280 |
| 13 | 3218159966 |
| 14 | 6646694992 |
| 15 | 13405336464 |
| 16 | 25160170656 |
| 17 | 46234874322 |
| 18 | 80560371528 |
| 19 | 137811490580 |
| 20 | 226332464440 |
| 21 | 365838595782 |