A143648-OEIS公司

A143648号作为一个简单的表

n个	a（n）
0	1
1	4
2	22
三	136
4	868
5	5584
6	35992
7	232096
8	1496848
9	9653824
10	62262112
11	401558656
12	2589848128
13	16703198464
14	107727106432
15	694784866816
16	4481007870208
17	28900214293504
18	186391635645952
19	1202130942232576
20	7753131181401088

[1,4,22,136,868,5584,35992,232096,1496848,9653824,62262112,401558656,2589848128,16703198464,107727106432,694784866816,4481007870208,28900214293504,186391635645952,1202130942232576,7753131181401088]