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 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 32 |
| 5 | 343 |
| 6 | 4505 |
| 7 | 66603 |
| 8 | 1045335 |
| 9 | 17115162 |
| 10 | 289107854 |
| 11 | 5007144433 |
| 12 | 88516438360 |
| 13 | 1591949961503 |
| 14 | 29053438148676 |
| 15 | 536972307386326 |
| 16 | 10034276171127780 |
| 17 | 189331187319203010 |
| 18 | 3603141751525175854 |
| 19 | 69097496637591215442 |
| 20 | 1334213677527481808220 |
| 21 | 25922717218623692348237 |