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 | 18 |
| 3 | 110 |
| 4 | 570 |
| 5 | 2702 |
| 6 | 12138 |
| 7 | 52670 |
| 8 | 223290 |
| 9 | 931502 |
| 10 | 3842058 |
| 11 | 15718430 |
| 12 | 63928410 |
| 13 | 258885902 |
| 14 | 1045076778 |
| 15 | 4208939390 |
| 16 | 16921719930 |
| 17 | 67944897902 |
| 18 | 272553908298 |
| 19 | 1092539107550 |
| 20 | 4377127901850 |
| 21 | 17529428119502 |
| 22 | 70180466208618 |
| 23 | 280910134414910 |
| 24 | 1124205363178170 |
| 25 | 4498515962822702 |