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 | 1 |
| 2 | 5 |
| 3 | 32 |
| 4 | 254 |
| 5 | 2414 |
| 6 | 26746 |
| 7 | 338568 |
| 8 | 4820952 |
| 9 | 76270032 |
| 10 | 1327263024 |
| 11 | 25196689968 |
| 12 | 518190651744 |
| 13 | 11476753967184 |
| 14 | 272339818023984 |
| 15 | 6893370154797312 |
| 16 | 185387657162396544 |
| 17 | 5279022594143270784 |
| 18 | 158674547929990485888 |
| 19 | 5020389181983702415104 |
| 20 | 166784921186052433648896 |