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 | 129 |
| 4 | 665 |
| 5 | 3425 |
| 6 | 17641 |
| 7 | 90865 |
| 8 | 468025 |
| 9 | 2410689 |
| 10 | 12416905 |
| 11 | 63956625 |
| 12 | 329425881 |
| 13 | 1696797025 |
| 14 | 8739811625 |
| 15 | 45016761649 |
| 16 | 231870996345 |
| 17 | 1194314228225 |
| 18 | 6151638187721 |
| 19 | 31685674923985 |
| 20 | 163205631532825 |