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 | 0 |
| 3 | 2 |
| 4 | 7 |
| 5 | 24 |
| 6 | 84 |
| 7 | 300 |
| 8 | 1089 |
| 9 | 4004 |
| 10 | 14872 |
| 11 | 55692 |
| 12 | 209950 |
| 13 | 795872 |
| 14 | 3031032 |
| 15 | 11589240 |
| 16 | 44462565 |
| 17 | 171085500 |
| 18 | 660009840 |
| 19 | 2551955340 |
| 20 | 9887121090 |
| 21 | 38374857840 |
| 22 | 149184555000 |
| 23 | 580807904040 |
| 24 | 2264193450090 |
| 25 | 8837215647624 |
| 26 | 34529741789904 |
| 27 | 135054066707000 |