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 | 0 |
| 1 | 2 |
| 2 | 9 |
| 3 | 52 |
| 4 | 335 |
| 5 | 2466 |
| 6 | 20447 |
| 7 | 189064 |
| 8 | 1930959 |
| 9 | 21603430 |
| 10 | 262869959 |
| 11 | 3457226268 |
| 12 | 48880169351 |
| 13 | 739429561066 |
| 14 | 11918051268255 |
| 15 | 203914545928336 |
| 16 | 3691384616598047 |
| 17 | 70491995143458894 |
| 18 | 1416242276574905879 |
| 19 | 29862732908481855460 |
| 20 | 659413025994777460119 |