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 | 3 |
| 2 | 12 |
| 3 | 39 |
| 4 | 132 |
| 5 | 456 |
| 6 | 1572 |
| 7 | 5409 |
| 8 | 18612 |
| 9 | 64053 |
| 10 | 220440 |
| 11 | 758640 |
| 12 | 2610840 |
| 13 | 8985147 |
| 14 | 30922188 |
| 15 | 106418031 |
| 16 | 366235308 |
| 17 | 1260390744 |
| 18 | 4337606988 |
| 19 | 14927778921 |
| 20 | 51373622388 |
| 21 | 176801189997 |
| 22 | 608457401520 |
| 23 | 2093992746720 |
| 24 | 7206429919920 |
| 25 | 24800769855603 |
| 26 | 85351303248012 |