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 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 54 |
| 4 | 201 |
| 5 | 672 |
| 6 | 2268 |
| 7 | 7266 |
| 8 | 23208 |
| 9 | 72414 |
| 10 | 224652 |
| 11 | 688929 |
| 12 | 2103975 |
| 13 | 6386907 |
| 14 | 19337091 |
| 15 | 58367817 |
| 16 | 175905741 |
| 17 | 529331190 |
| 18 | 1591515297 |
| 19 | 4781575074 |
| 20 | 14359673454 |
| 21 | 43108645230 |
| 22 | 129387584991 |
| 23 | 388283978589 |
| 24 | 1165099808574 |
| 25 | 3495782937135 |
| 26 | 10488322595625 |