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 | 7 |
| 2 | 33 |
| 3 | 129 |
| 4 | 450 |
| 5 | 1452 |
| 6 | 4424 |
| 7 | 12896 |
| 8 | 36288 |
| 9 | 99200 |
| 10 | 264704 |
| 11 | 691968 |
| 12 | 1777152 |
| 13 | 4494336 |
| 14 | 11212800 |
| 15 | 27639808 |
| 16 | 67403776 |
| 17 | 162791424 |
| 18 | 389742592 |
| 19 | 925696000 |
| 20 | 2182742016 |
| 21 | 5112594432 |
| 22 | 11901861888 |
| 23 | 27550285824 |
| 24 | 63438848000 |
| 25 | 145366188032 |
| 26 | 331584897024 |
| 27 | 753146003456 |
| 28 | 1703860502528 |