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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 12 |
| 3 | 36 |
| 4 | 96 |
| 5 | 264 |
| 6 | 696 |
| 7 | 1848 |
| 8 | 4848 |
| 9 | 12768 |
| 10 | 33480 |
| 11 | 87936 |
| 12 | 230520 |
| 13 | 604608 |
| 14 | 1585128 |
| 15 | 4156392 |
| 16 | 10895952 |
| 17 | 28566216 |
| 18 | 74887056 |
| 19 | 196322976 |
| 20 | 514662960 |
| 21 | 1349208600 |
| 22 | 3536962584 |
| 23 | 9272217936 |
| 24 | 24307198464 |
| 25 | 63721617888 |
| 26 | 167046745992 |
| 27 | 437914664688 |
| 28 | 1147996820376 |
| 29 | 3009483583056 |
| 30 | 7889385389784 |
| 31 | 20682088837608 |
| 32 | 54218261608896 |
[1,4,12,36,96,264,696,1848,4848,12768,33480,87936, 230520,604608,1585128,4156392,10895952,28566216, 74887056,196322976,514662960,1349208600, 3536962584,9272217936,24307198464,63721617888, 167046745992,437914664688,1147996820376, 3009483583056,7889385389784,20682088837608, 54218261608896] |