A278426 - OEIS

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A278426 as a simple table

n	a(n)
1	1
2	3
3	4
4	13
5	15
6	21
7	27
8	63
9	70
10	123
11	136
12	178
13	208
14	265
15	411
16	457
17	856
18	2401
19	4642
20	8017
21	8211
22	8385
23	12337
24	20793
25	123970
26	189928

[1,3,4,13,15,21,27,63,70,123,136,178,208,265,411, 457,856,2401,4642,8017,8211,8385,12337,20793, 123970,189928]