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 | 9 |
| 2 | 51 |
| 3 | 233 |
| 4 | 942 |
| 5 | 3522 |
| 6 | 12473 |
| 7 | 42447 |
| 8 | 140109 |
| 9 | 451441 |
| 10 | 1426380 |
| 11 | 4434420 |
| 12 | 13599505 |
| 13 | 41225349 |
| 14 | 123723351 |
| 15 | 368080793 |
| 16 | 1086665562 |
| 17 | 3186317718 |
| 18 | 9286256393 |
| 19 | 26916587307 |
| 20 | 77634928209 |
| 21 | 222920650081 |