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 | 4 |
| 2 | 16 |
| 3 | 58 |
| 4 | 204 |
| 5 | 712 |
| 6 | 2490 |
| 7 | 8770 |
| 8 | 31200 |
| 9 | 112300 |
| 10 | 409254 |
| 11 | 1510102 |
| 12 | 5638956 |
| 13 | 21290368 |
| 14 | 81183858 |
| 15 | 312262954 |
| 16 | 1210023672 |
| 17 | 4718194516 |
| 18 | 18492663102 |
| 19 | 72787129726 |
| 20 | 287468548548 |
| 21 | 1138446338344 |
| 22 | 4518338475786 |
| 23 | 17963524388818 |
| 24 | 71514144464784 |