cp's OEIS Frontend

A316992 Numbers m such that 1 < gcd(m, 15) < m and m does not divide 15^e for e >= 0.

%I A316992 #13 Aug 15 2018 22:22:17
%S A316992 6,10,12,18,20,21,24,30,33,35,36,39,40,42,48,50,51,54,55,57,60,63,65,
%T A316992 66,69,70,72,78,80,84,85,87,90,93,95,96,99,100,102,105,108,110,111,
%U A316992 114,115,117,120,123,126,129,130,132,138,140,141,144,145,147,150
%N A316992 Numbers m such that 1 < gcd(m, 15) < m and m does not divide 15^e for e >= 0.
%C A316992 Complement of A000027 and union of A003593 and A229829.
%C A316992 Analogous to A081062 and A105115 that apply to A120944(1)=6 and A120944(2)=10, respectively.
%C A316992 This sequence applies to term A120944(4)=15.
%H A316992 Michael De Vlieger, <a href="/A316992/b316992.txt">Table of n, a(n) for n = 1..10000</a>
%e A316992 6 is in the sequence since gcd(6, 15) = 3 and 6 does not divide 15^e with integer e >= 0.
%e A316992 2 and 4 are not in the sequence since they are coprime to 15.
%e A316992 3 and 5 are not in the sequence since they are divisors of 15.
%e A316992 9 is not in the sequence since 9 | 15^2.
%t A316992 With[{nn = 150, k = 15}, Select[Range@ nn, And[1 < GCD[#, k] < #, PowerMod[k, Floor@ Log2@ nn, #] != 0] &]]
%Y A316992 Cf. A003593, A081062, A105115, A120944, A229829, A316991.
%K A316992 easy,nonn
%O A316992 1,1
%A A316992 _Michael De Vlieger_, Aug 02 2018