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 | 4 |
| 2 | 12 |
| 3 | 34 |
| 4 | 78 |
| 5 | 180 |
| 6 | 408 |
| 7 | 900 |
| 8 | 2052 |
| 9 | 4490 |
| 10 | 9702 |
| 11 | 21010 |
| 12 | 45144 |
| 13 | 96486 |
| 14 | 205590 |
| 15 | 435548 |
| 16 | 920896 |
| 17 | 1938594 |
| 18 | 4072946 |
| 19 | 8535970 |
| 20 | 17845982 |
| 21 | 37242540 |
| 22 | 77569570 |
| 23 | 161300102 |
| 24 | 334906956 |
| 25 | 694329000 |
| 26 | 1437620932 |
| 27 | 2972973918 |
| 28 | 6141189354 |
| 29 | 12672042908 |
| 30 | 26122458858 |
| 31 | 53799031890 |