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 | 3 |
| 1 | 15 |
| 2 | 105 |
| 3 | 315 |
| 4 | 6930 |
| 5 | 18018 |
| 6 | 90090 |
| 7 | 218790 |
| 8 | 2078505 |
| 9 | 4849845 |
| 10 | 22309287 |
| 11 | 50702925 |
| 12 | 1825305300 |
| 13 | 4071834900 |
| 14 | 18032411700 |
| 15 | 39671305740 |
| 16 | 347123925225 |
| 17 | 755505013725 |
| 18 | 3273855059475 |
| 19 | 7064634602025 |
| 20 | 121511715154830 |
| 21 | 260382246760350 |
| 22 | 1112542327066950 |
| 23 | 2370198870707850 |
| 24 | 20146690401016725 |