A228019 - OEIS

%I #25 Sep 08 2022 08:46:05

%S 4,6,8,9,15,18,22,24,26,27,28,33,35,36,39,40,42,44,45,46,48,51,54,55,

%T 57,60,62,63,64,66,68,69,72,75,77,78,80,81,82,84,86,87,88,90,91,93,95,

%U 96,99,105,108,112,114,116,117,118,121,123,125,126,129,130,132

%N Composite numbers whose sum of digits is a composite number.

%H Charles R Greathouse IV, <a href="/A228019/b228019.txt">Table of n, a(n) for n = 1..10000</a>

%e 87 is a term: 87 and 8+7=15 are composite.

%o (PARI) lista(N) = my(s); for(n=2,N, s=sumdigits(n); if(!isprime(n)&&!isprime(s)&&s>1, print1(n,", ") ) ) \\ _Joerg Arndt_, Aug 04 2013

%o (PARI) list(N)=my(v=List(),s); forcomposite(n=4,N,s=sumdigits(n); if(s>1 && !isprime(s), listput(v,n))); Vec(v)  \\ _Charles R Greathouse IV_, Aug 13 2013

%o (Magma) [n: n in [4..200] | not IsPrime(n) and not IsPrime(&+Intseq(n))]; // _Bruno Berselli_, Aug 13 2013

%Y Subsequence of A104211.

%K nonn,base,easy

%O 1,1

%A _Derek Orr_, Aug 02 2013