A250045 - OEIS

%I #18 Jan 29 2015 09:48:34

%S 2,3,4,5,6,7,16,18,20,22,24,27,30,32,34,36,38,40,45,48,50,51,52,54,56,

%T 63,128,130,132,134,144,146,147,148,150,160,162,164,165,166,176,178,

%U 180,182,192,194,195,196,198,216,219,222,240,242,243,244,245,246

%N Numbers n such that m = floor(n/8) 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=8. In particular, they define the property RTNC(b).

%H Stanislav Sykora, <a href="/A250045/b250045.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 the link

%o (PARI) is_rtnc(n, b=8) = {while (((m=gcd(n\b, n)) != 1), if (m == 0, return (1)); n = n\b; ); return (0); } \\ _Michel Marcus_, Jan 22 2015

%Y Cf. A250041 (b=10), A250044.

%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), A250047 (b=7), A250049 (b=6), A250051 (b=5).

%K nonn,base

%O 1,1

%A _Stanislav Sykora_, Jan 15 2015