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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 0 |
| 5 | 3 |
| 6 | 2 |
| 7 | 12 |
| 8 | 18 |
| 9 | 65 |
| 10 | 138 |
| 11 | 432 |
| 12 | 1074 |
| 13 | 3231 |
| 14 | 8718 |
| 15 | 25999 |
| 16 | 73650 |
| 17 | 220215 |
| 18 | 643546 |
| 19 | 1937877 |
| 20 | 5783700 |
| 21 | 17564727 |
| 22 | 53222094 |
| 23 | 163009086 |
| 24 | 499634508 |
| 25 | 1542392088 |
| 26 | 4770925446 |
| 27 | 14832934031 |
| 28 | 46227584010 |
| 29 | 144632622552 |
| 30 | 453628244950 |