A250051 - OEIS

%I #7 Feb 06 2015 05:52:27

%S 2,3,4,10,12,14,15,18,20,22,24,50,52,54,60,62,63,64,70,72,74,75,78,90,

%T 92,93,94,100,102,104,110,112,114,120,122,123,124,250,252,254,260,262,

%U 264,270,272,273,274,300,302,303,304,310,312,314,315,318

%N Numbers n such that m = floor(n/5) is not coprime to n and, if nonzero, m is also a term of the sequence.

%C See the comments in A250041 which all apply, except for the setting of the base, b=5. In particular, they define the property RTNC(b).

%H Stanislav Sykora, <a href="/A250051/b250051.txt">Table of n, a(n) for n = 1..10000</a>

%H Stanislav Sykora, <a href="https://oeis.org/wiki/File:GeneticThreads.txt">PARI/GP scripts for genetic threads</a>, with code and comments.

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Coprime_integers">Coprime integers</a>

%o (PARI) \\ See A250041 for b=5

%o (PARI) is_rtnc(n, b=5) = {while (((m=gcd(n\b, n)) != 1), if (m == 0, return (1)); n = n\b;); return (0);} \\ _Michel Marcus_, Jan 31 2015

%Y Cf. A250041 (b=10), A250046.

%Y Other lists of right-truncatable numbers with the property RTNC(b):

%Y A005823 (b=3), A250037 (b=4), A250039 (b=16), A250043 (b=9), A250045 (b=8), A250047 (b=7), A250049 (b=6).

%K nonn,base

%O 1,1

%A _Stanislav Sykora_, Jan 31 2015