A014521 - OEIS

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A014521 as a simple table

n	a(n)
0	2
1	1
2	1
3	3
4	12
5	52
6	288
7	1871
8	14034
9	119292
10	1133278
11	11899423
12	136843365
13	1710542068
14	23092317922
15	334838609874
16	5189998453040
17	85634974475162
18	1498612053315336
19	27724322986333718
20	540624298233507504

[2,1,1,3,12,52,288,1871,14034,119292,1133278, 11899423,136843365,1710542068,23092317922, 334838609874,5189998453040,85634974475162, 1498612053315336,27724322986333718, 540624298233507504]