A271217 - OEIS

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A271217 as a simple table

n	a(n)
0	1
1	2
2	2
3	6
4	22
5	50
6	274
7	598
8	4486
9	9570
10	90914
11	191398
12	2201078
13	4593554
14	62012978
15	128619510
16	1993602406
17	4115824322
18	72026925634
19	148169675590
20	2889308674006

[1,2,2,6,22,50,274,598,4486,9570,90914,191398, 2201078,4593554,62012978,128619510,1993602406, 4115824322,72026925634,148169675590,2889308674006]