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 | 4 |
| 2 | 18 |
| 3 | 80 |
| 4 | 355 |
| 5 | 1580 |
| 6 | 7066 |
| 7 | 31772 |
| 8 | 143645 |
| 9 | 652860 |
| 10 | 2981910 |
| 11 | 13682328 |
| 12 | 63046776 |
| 13 | 291646860 |
| 14 | 1353967250 |
| 15 | 6306552800 |
| 16 | 29464361530 |
| 17 | 138045441260 |
| 18 | 648449195350 |
| 19 | 3053348997200 |
| 20 | 14409512770575 |
| 21 | 68143962854836 |
| 22 | 322886537205062 |
| 23 | 1532716400556220 |
| 24 | 7288075248828605 |
| 25 | 34710221395625380 |