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A228019
Composite numbers whose sum of digits is a composite number.
4
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
1,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
87 is a term: 87 and 8+7=15 are composite.
PROG
(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
(Magma) [n: n in [4..200] | not IsPrime(n) and not IsPrime(&+Intseq(n))]; // Bruno Berselli, Aug 13 2013
CROSSREFS
Subsequence of A104211.
Sequence in context: A262389 A254755 A275624 * A228020 A163282 A095404
KEYWORD
nonn,base,easy
AUTHOR
Derek Orr, Aug 02 2013
STATUS
approved