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 | 5 |
| 2 | 25 |
| 3 | 125 |
| 4 | 625 |
| 5 | 3120 |
| 6 | 15580 |
| 7 | 77800 |
| 8 | 388500 |
| 9 | 1940000 |
| 10 | 9687520 |
| 11 | 48375280 |
| 12 | 241565200 |
| 13 | 1206272000 |
| 14 | 6023600000 |
| 15 | 30079249920 |
| 16 | 150202748480 |
| 17 | 750047481600 |
| 18 | 3745412320000 |
| 19 | 18702967200000 |
| 20 | 93394519000320 |
| 21 | 466371784007680 |
| 22 | 2328858730112000 |
| 23 | 11629312001280000 |
| 24 | 58071748137600000 |
| 25 | 289985162611998720 |
| 26 | 1448060325923962880 |
| 27 | 7230986194699366400 |