A180677 - OEIS

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A180677 as a simple table

n	a(n)
0	1
1	3
2	15
3	87
4	503
5	2871
6	16311
7	92599
8	525751
9	2985399
10	16952759
11	96267703
12	546663863
13	3104271799
14	17627835831
15	100100959671
16	568430652855
17	3227875241399
18	18329726840247
19	104086701305271
20	591063984860599

[1,3,15,87,503,2871,16311,92599,525751,2985399, 16952759,96267703,546663863,3104271799, 17627835831,100100959671,568430652855, 3227875241399,18329726840247,104086701305271, 591063984860599]

[1,3,15,87,503,2871,16311,92599,525751,2985399,
 16952759,96267703,546663863,3104271799,
 17627835831,100100959671,568430652855,
 3227875241399,18329726840247,104086701305271,
 591063984860599]