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 | 1 |
| 2 | 5 |
| 3 | 21 |
| 4 | 87 |
| 5 | 363 |
| 6 | 1534 |
| 7 | 6570 |
| 8 | 28492 |
| 9 | 124944 |
| 10 | 553301 |
| 11 | 2471373 |
| 12 | 11122275 |
| 13 | 50389695 |
| 14 | 229643895 |
| 15 | 1052093655 |
| 16 | 4842863465 |
| 17 | 22386911925 |
| 18 | 103885321615 |
| 19 | 483759492255 |
| 20 | 2259888333445 |
| 21 | 10587902977185 |
| 22 | 49738841822400 |
| 23 | 234235771140876 |
| 24 | 1105609645231322 |
| 25 | 5229610939919718 |