A180642 - cp's OEIS frontend

A180642 Numbers k such that phi(k)/4 is a prime, where phi is the Euler totient function.

n	a(n)
1	13
2	15
3	16
4	20
5	21
6	24
7	25
8	26
9	28
10	29
11	30
12	33
13	36
14	42
15	44
16	50
17	53
18	58
19	66
20	69
21	92
22	106
23	138
24	141
25	149
26	173
27	177
28	188
29	236
30	249
31	269
32	282
33	293
34	298
35	317
36	321
37	332
38	346
39	354
40	389
41	428
42	498
43	501
44	509
45	537
46	538
47	557
48	586
49	634
50	642
51	653
52	668
53	681
54	716
55	773
56	778
57	789

[13, 15, 16, 20, 21, 24, 25, 26, 28, 29, 30, 33, 36, 42, 44, 50, 53, 58, 66, 69, 92, 106, 138, 141, 149, 173, 177, 188, 236, 249, 269, 282, 293, 298, 317, 321, 332, 346, 354, 389, 428, 498, 501, 509, 537, 538, 557, 586, 634, 642, 653, 668, 681, 716, 773, 778, 789]

cp's OEIS Frontend

A180642 Numbers k such that phi(k)/4 is a prime, where phi is the Euler totient function.

Table of values

List of values

n	a(n)
1	13
2	15
3	16
4	20
5	21
6	24
7	25
8	26
9	28
10	29
11	30
12	33
13	36
14	42
15	44
16	50
17	53
18	58
19	66
20	69
21	92
22	106
23	138
24	141
25	149
26	173
27	177
28	188
29	236
30	249
31	269
32	282
33	293
34	298
35	317
36	321
37	332
38	346
39	354
40	389
41	428
42	498
43	501
44	509
45	537
46	538
47	557
48	586
49	634
50	642
51	653
52	668
53	681
54	716
55	773
56	778
57	789

n	a(n)
1	13
2	15
3	16
4	20
5	21
6	24
7	25
8	26
9	28
10	29
11	30
12	33
13	36
14	42
15	44
16	50
17	53
18	58
19	66
20	69
21	92
22	106
23	138
24	141
25	149
26	173
27	177
28	188
29	236
30	249
31	269
32	282
33	293
34	298
35	317
36	321
37	332
38	346
39	354
40	389
41	428
42	498
43	501
44	509
45	537
46	538
47	557
48	586
49	634
50	642
51	653
52	668
53	681
54	716
55	773
56	778
57	789

n	a(n)
1	13
2	15
3	16
4	20
5	21
6	24
7	25
8	26
9	28
10	29
11	30
12	33
13	36
14	42
15	44
16	50
17	53
18	58
19	66
20	69
21	92
22	106
23	138
24	141
25	149
26	173
27	177
28	188
29	236
30	249
31	269
32	282
33	293
34	298
35	317
36	321
37	332
38	346
39	354
40	389
41	428
42	498
43	501
44	509
45	537
46	538
47	557
48	586
49	634
50	642
51	653
52	668
53	681
54	716
55	773
56	778
57	789