A133580 - cp's OEIS frontend

A133580 a(0)=a(1)=1; for n>1, a(n) = 2*a(n-1) + 1 if a(n-1) and n are coprime, otherwise a(n) = a(n-1)/gcd(a(n-1),n).

n	a(n)
0	1
1	1
2	3
3	1
4	3
5	7
6	15
7	31
8	63
9	7
10	15
11	31
12	63
13	127
14	255
15	17
16	35
17	71
18	143
19	287
20	575
21	1151
22	2303
23	4607
24	9215
25	1843
26	3687
27	1229
28	2459
29	4919
30	9839
31	19679
32	39359
33	78719
34	157439
35	314879
36	629759
37	1259519
38	2519039
39	5038079
40	10076159
41	20152319
42	40304639

[1, 1, 3, 1, 3, 7, 15, 31, 63, 7, 15, 31, 63, 127, 255, 17, 35, 71, 143, 287, 575, 1151, 2303, 4607, 9215, 1843, 3687, 1229, 2459, 4919, 9839, 19679, 39359, 78719, 157439, 314879, 629759, 1259519, 2519039, 5038079, 10076159, 20152319, 40304639]

cp's OEIS Frontend

A133580 a(0)=a(1)=1; for n>1, a(n) = 2*a(n-1) + 1 if a(n-1) and n are coprime, otherwise a(n) = a(n-1)/gcd(a(n-1),n).

Table of values

List of values