A357215 - OEIS

A357215 as a simple table

n	a(n)
1	0
2	1
3	3
4	3
5	7
6	7
7	15
8	15
9	15
10	15
11	31
12	31
13	63
14	63
15	63
16	63
17	127
18	127
19	255
20	255
21	255
22	255
23	511
24	511
25	511
26	511
27	511
28	511
29	1023
30	1023
31	2047
32	2047
33	2047
34	2047
35	2047
36	2047
37	4095
38	4095
39	4095
40	4095
41	8191
42	8191
43	16383
44	16383
45	16383
46	16383
47	32767
48	32767
49	32767
50	32767

[0,1,3,3,7,7,15,15,15,15,31,31,63,63,63,63,127, 127,255,255,255,255,511,511,511,511,511,511,1023, 1023,2047,2047,2047,2047,2047,2047,4095,4095,4095, 4095,8191,8191,16383,16383,16383,16383,32767, 32767,32767,32767]