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 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 32 |
| 5 | 120 |
| 6 | 513 |
| 7 | 2455 |
| 8 | 13040 |
| 9 | 76440 |
| 10 | 492231 |
| 11 | 3465163 |
| 12 | 26530503 |
| 13 | 219754535 |
| 14 | 1959181266 |
| 15 | 18710532565 |
| 16 | 190588702776 |
| 17 | 2062664376064 |
| 18 | 23636408157551 |
| 19 | 285900639990875 |
| 20 | 3640199365715769 |
| 21 | 48665876423760247 |