A228019 Composite numbers whose sum of digits is a composite number.

4, 6, 8, 9, 15, 18, 22, 24, 26, 27, 28, 33, 35, 36, 39, 40, 42, 44, 45, 46, 48, 51, 54, 55, 57, 60, 62, 63, 64, 66, 68, 69, 72, 75, 77, 78, 80, 81, 82, 84, 86, 87, 88, 90, 91, 93, 95, 96, 99, 105, 108, 112, 114, 116, 117, 118, 121, 123, 125, 126, 129, 130, 132

Offset: 1

Author

Derek Orr, Aug 02 2013

Keywords

• nonn
• base
• easy

Examples

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

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A104211.

Programs

Magma

[n: n in [4..200] | not IsPrime(n) and not IsPrime(&+Intseq(n))]; // Bruno Berselli, Aug 13 2013

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

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