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 | 150 |
| 4 | 726 |
| 5 | 3510 |
| 6 | 16710 |
| 7 | 79494 |
| 8 | 375174 |
| 9 | 1769686 |
| 10 | 8306862 |
| 11 | 38975286 |
| 12 | 182265822 |
| 13 | 852063558 |
| 14 | 3973784886 |
| 15 | 18527532310 |
| 16 | 86228667894 |
| 17 | 401225368086 |
| 18 | 1864308847838 |
| 19 | 8660961643254 |
| 20 | 40190947325670 |
| 21 | 186475398518726 |
| 22 | 864404776466406 |
| 23 | 4006394107568934 |
| 24 | 18554916271112254 |
| 25 | 85923704942057238 |