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%I #14 Dec 28 2018 11:55:13
%S 4,8,4,6,4,4,4,8,4,6,4,4,4,8,4,6,4,4,4,6,4,4,4,4,4,8,4,6,4,4,4,4,4,6,
%T 4,4,4,8,4,6,4,4,4,6,4,4,4,4,4,6,4,4,4,4,4,8,4,6,4,4,4,4,4,6,4,4,4,8,
%U 4,6,4,4,4,4,4,6,4,4,4,6,4,4,4,4,4,6,4,4,4,4,4,4,4,6,4,4,4,8,4,6,4
%N Smallest positive composite number such that a(n)+n is also composite.
%C a(0)=4. Adding a(0) to n=0 gives 4+0=4, which is a composite number; adding a(1) to n=1 gives 8+1=9 which is composite; adding a(2) to n=2 gives 4+2=6 which is composite; adding a(3) to n=3 gives 6+3=9 which is composite; etc.
%C At least one of {n+4, n+6, n+8} is divisible by 3, so a(n) is in {4,6,8} for all n. - _Charlie Neder_, Dec 28 2018
%H Charlie Neder, <a href="/A155874/b155874.txt">Table of n, a(n) for n = 0..1000</a>
%F If n+4 is in A001359, a(n) = 8. If n+4 is in A067774, a(n) = 6. Otherwise, a(n) = 4. - _Charlie Neder_, Dec 28 2018
%o (PARI) a(n) = {forcomposite(k=4, 10, if (!isprime(k+n), return(k)););} \\ _Michel Marcus_, Dec 28 2018
%Y Cf. A122984.
%K easy,nonn
%O 0,1
%A _Eric Angelini_, Jan 29 2009
%E More terms from _Charlie Neder_, Dec 28 2018
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