A178174 - cp's OEIS frontend

A178174 a(1)=a(2)=a(3)=a(4)=1; thereafter a(n) = gpf(a(n-1)+a(n-2)+a(n-3)+a(n-4)), where gpf is the greatest prime factor.

n	a(n)
1	1
2	1
3	1
4	1
5	2
6	5
7	3
8	11
9	7
10	13
11	17
12	3
13	5
14	19
15	11
16	19
17	3
18	13
19	23
20	29
21	17
22	41
23	11
24	7
25	19
26	13
27	5
28	11
29	3
30	2
31	7
32	23
33	7
34	13
35	5
36	3
37	7
38	7
39	11
40	7
41	2
42	3
43	23
44	7
45	7
46	5
47	7
48	13
49	2
50	3
51	5
52	23
53	11
54	7
55	23
56	2
57	43
58	5
59	73
60	41
61	3
62	61
63	89
64	97
65	5
66	7
67	11
68	5
69	7
70	5
71	7
72	3
73	11
74	13
75	17
76	11
77	13
78	3
79	11
80	19
81	23
82	7
83	5
84	3
85	19
86	17
87	11
88	5
89	13
90	23
91	13
92	3
93	13
94	13
95	7
96	3
97	3
98	13
99	13
100	2
101	31
102	59
103	7
104	11
105	3
106	5
107	13
108	2
109	23
110	43
111	3
112	71
113	7
114	31

[1, 1, 1, 1, 2, 5, 3, 11, 7, 13, 17, 3, 5, 19, 11, 19, 3, 13, 23, 29, 17, 41, 11, 7, 19, 13, 5, 11, 3, 2, 7, 23, 7, 13, 5, 3, 7, 7, 11, 7, 2, 3, 23, 7, 7, 5, 7, 13, 2, 3, 5, 23, 11, 7, 23, 2, 43, 5, 73, 41, 3, 61, 89, 97, 5, 7, 11, 5, 7, 5, 7, 3, 11, 13, 17, 11, 13, 3, 11, 19, 23, 7, 5, 3, 19, 17, 11, 5, 13, 23, 13, 3, 13, 13, 7, 3, 3, 13, 13, 2, 31, 59, 7, 11, 3, 5, 13, 2, 23, 43, 3, 71, 7, 31]

cp's OEIS Frontend

A178174 a(1)=a(2)=a(3)=a(4)=1; thereafter a(n) = gpf(a(n-1)+a(n-2)+a(n-3)+a(n-4)), where gpf is the greatest prime factor.

Table of values

List of values

n	a(n)
1	1
2	1
3	1
4	1
5	2
6	5
7	3
8	11
9	7
10	13
11	17
12	3
13	5
14	19
15	11
16	19
17	3
18	13
19	23
20	29
21	17
22	41
23	11
24	7
25	19
26	13
27	5
28	11
29	3
30	2
31	7
32	23
33	7
34	13
35	5
36	3
37	7
38	7
39	11
40	7
41	2
42	3
43	23
44	7
45	7
46	5
47	7
48	13
49	2
50	3
51	5
52	23
53	11
54	7
55	23
56	2
57	43
58	5
59	73
60	41
61	3
62	61
63	89
64	97
65	5
66	7
67	11
68	5
69	7
70	5
71	7
72	3
73	11
74	13
75	17
76	11
77	13
78	3
79	11
80	19
81	23
82	7
83	5
84	3
85	19
86	17
87	11
88	5
89	13
90	23
91	13
92	3
93	13
94	13
95	7
96	3
97	3
98	13
99	13
100	2
101	31
102	59
103	7
104	11
105	3
106	5
107	13
108	2
109	23
110	43
111	3
112	71
113	7
114	31

n	a(n)
1	1
2	1
3	1
4	1
5	2
6	5
7	3
8	11
9	7
10	13
11	17
12	3
13	5
14	19
15	11
16	19
17	3
18	13
19	23
20	29
21	17
22	41
23	11
24	7
25	19
26	13
27	5
28	11
29	3
30	2
31	7
32	23
33	7
34	13
35	5
36	3
37	7
38	7
39	11
40	7
41	2
42	3
43	23
44	7
45	7
46	5
47	7
48	13
49	2
50	3
51	5
52	23
53	11
54	7
55	23
56	2
57	43
58	5
59	73
60	41
61	3
62	61
63	89
64	97
65	5
66	7
67	11
68	5
69	7
70	5
71	7
72	3
73	11
74	13
75	17
76	11
77	13
78	3
79	11
80	19
81	23
82	7
83	5
84	3
85	19
86	17
87	11
88	5
89	13
90	23
91	13
92	3
93	13
94	13
95	7
96	3
97	3
98	13
99	13
100	2
101	31
102	59
103	7
104	11
105	3
106	5
107	13
108	2
109	23
110	43
111	3
112	71
113	7
114	31

n	a(n)
1	1
2	1
3	1
4	1
5	2
6	5
7	3
8	11
9	7
10	13
11	17
12	3
13	5
14	19
15	11
16	19
17	3
18	13
19	23
20	29
21	17
22	41
23	11
24	7
25	19
26	13
27	5
28	11
29	3
30	2
31	7
32	23
33	7
34	13
35	5
36	3
37	7
38	7
39	11
40	7
41	2
42	3
43	23
44	7
45	7
46	5
47	7
48	13
49	2
50	3
51	5
52	23
53	11
54	7
55	23
56	2
57	43
58	5
59	73
60	41
61	3
62	61
63	89
64	97
65	5
66	7
67	11
68	5
69	7
70	5
71	7
72	3
73	11
74	13
75	17
76	11
77	13
78	3
79	11
80	19
81	23
82	7
83	5
84	3
85	19
86	17
87	11
88	5
89	13
90	23
91	13
92	3
93	13
94	13
95	7
96	3
97	3
98	13
99	13
100	2
101	31
102	59
103	7
104	11
105	3
106	5
107	13
108	2
109	23
110	43
111	3
112	71
113	7
114	31