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) |
|---|---|
| 1 | 2 |
| 2 | 10 |
| 3 | 54 |
| 4 | 228 |
| 5 | 990 |
| 6 | 3966 |
| 7 | 16254 |
| 8 | 65040 |
| 9 | 261576 |
| 10 | 1046550 |
| 11 | 4192254 |
| 12 | 16768860 |
| 13 | 67100670 |
| 14 | 268402806 |
| 15 | 1073708010 |
| 16 | 4294836480 |
| 17 | 17179738110 |
| 18 | 68718948984 |
| 19 | 274877382654 |
| 20 | 1099509531420 |
| 21 | 4398044397642 |
| 22 | 17592177657846 |
| 23 | 70368735789054 |
| 24 | 281474943095280 |