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 | 6 |
| 2 | 30 |
| 3 | 122 |
| 4 | 450 |
| 5 | 1518 |
| 6 | 4830 |
| 7 | 14586 |
| 8 | 42330 |
| 9 | 118622 |
| 10 | 322974 |
| 11 | 857298 |
| 12 | 2226586 |
| 13 | 5672046 |
| 14 | 14205654 |
| 15 | 35040722 |
| 16 | 85269114 |
| 17 | 204971478 |
| 18 | 487307542 |
| 19 | 1146995154 |
| 20 | 2675265522 |
| 21 | 6188176838 |
| 22 | 14205568950 |
| 23 | 32383725450 |
| 24 | 73352114450 |
| 25 | 165171276822 |
| 26 | 369904716750 |
| 27 | 824244212554 |