A318572 Squarefree numbers A005117(k) whose largest prime factor is not A318411(k).
35, 55, 70, 77, 95, 105, 110, 115, 119, 143, 154, 155, 161, 165, 187, 190, 203, 209, 210, 215, 221, 230, 231, 235, 238, 247, 253, 285, 286, 287, 295, 299, 310, 319, 322, 323, 329, 330, 335, 345, 355, 357, 371, 374, 377, 385, 391, 395, 403, 406, 407, 413, 415, 418, 429, 430
Offset: 1
Keywords
Examples
A005117(k) is the k-th squarefree number.
A073482(k) is the largest prime factor of A005117(k).
A073482(k) = A318411(k) for 2 <= k <= 22.
-------+------------+------------+------------
k | A005117(k) | A073482(k) | A318411(k)
-------+------------+------------+------------
23 | 35 | 7 | 13
34 | 55 | 11 | 21
44 | 70 | 7 | 13
48 | 77 | 11 | 31
60 | 95 | 19 | 37
65 | 105 | 7 | 13
69 | 110 | 11 | 21
73 | 115 | 23 | 45
75 | 119 | 17 | 49
89 | 143 | 13 | 61
94 | 154 | 11 | 31
95 | 155 | 31 | 61
99 | 161 | 23 | 67
101 | 165 | 11 | 21
115 | 187 | 17 | 81
116 | 190 | 19 | 37
Links
- Seiichi Manyama, Table of n, a(n) for n = 1..5000
Programs
-
Ruby
require 'prime' def A(n) s = 1 flag = false while !flag s += 1 flag = true (1..n - 1).each{|i| if i != ((i ** s) % n) flag = false break end } end s end def A318572(n) ary = [] i = 2 while ary.size < n pq = i.prime_division if pq.all?{|j| j[1] == 1} ary << i if A(i) != pq[-1][0] end i += 1 end ary end p A318572(50)