A347475 - cp's OEIS frontend

A347475 Numbers k such that k and the k-th triangular number T(k) = k*(k+1)/2 have only odd digits.

n	a(n)
1	1
2	5
3	13
4	17
5	177
6	1777
7	3937
8	5537
9	5573
10	15173
11	55377
12	55733
13	79137
14	135173
15	195937
16	339173
17	377777
18	399377
19	791377
20	3397973
21	5199137
22	7913777
23	13535137
24	17397537
25	33993973
26	37735377
27	39993777
28	59591173
29	59919137
30	79971937
31	135157537
32	139713973
33	153177777

[1, 5, 13, 17, 177, 1777, 3937, 5537, 5573, 15173, 55377, 55733, 79137, 135173, 195937, 339173, 377777, 399377, 791377, 3397973, 5199137, 7913777, 13535137, 17397537, 33993973, 37735377, 39993777, 59591173, 59919137, 79971937, 135157537, 139713973, 153177777]

cp's OEIS Frontend

A347475 Numbers k such that k and the k-th triangular number T(k) = k*(k+1)/2 have only odd digits.

Table of values

List of values