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 | 0 |
| 1 | 2 |
| 2 | 12 |
| 3 | 54 |
| 4 | 230 |
| 5 | 948 |
| 6 | 3860 |
| 7 | 15624 |
| 8 | 63014 |
| 9 | 253588 |
| 10 | 1019072 |
| 11 | 4091174 |
| 12 | 16412668 |
| 13 | 65808044 |
| 14 | 263755984 |
| 15 | 1056789662 |
| 16 | 4233176854 |
| 17 | 16953418148 |
| 18 | 67885557896 |
| 19 | 271793651816 |
| 20 | 1088059997732 |
| 21 | 4355377285932 |
| 22 | 17432688395816 |
| 23 | 69770793302408 |
| 24 | 279227252601884 |