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 | 4 |
| 3 | 15 |
| 4 | 57 |
| 5 | 220 |
| 6 | 859 |
| 7 | 3381 |
| 8 | 13380 |
| 9 | 53143 |
| 10 | 211585 |
| 11 | 843756 |
| 12 | 3368259 |
| 13 | 13455325 |
| 14 | 53774932 |
| 15 | 214978335 |
| 16 | 859595529 |
| 17 | 3437550076 |
| 18 | 13748021995 |
| 19 | 54986385093 |
| 20 | 219930610020 |
| 21 | 879683351911 |
| 22 | 3518631073489 |
| 23 | 14074256379660 |
| 24 | 56296324109907 |
| 25 | 225183460127725 |
| 26 | 900729032983924 |