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 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 18 |
| 5 | 71 |
| 6 | 252 |
| 7 | 1001 |
| 8 | 4540 |
| 9 | 18089 |
| 10 | 99990 |
| 11 | 398959 |
| 12 | 2602278 |
| 13 | 10391023 |
| 14 | 78132152 |
| 15 | 312129649 |
| 16 | 2658297528 |
| 17 | 10622799089 |
| 18 | 101072656170 |
| 19 | 403978495031 |
| 20 | 4247085597370 |
| 21 | 16977719590391 |
| 22 | 195445764537012 |
| 23 | 781379079653017 |
| 24 | 9775727355457908 |
| 25 | 39085931702241241 |
| 26 | 528050767520083262 |
| 27 | 2111421691000680031 |