This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A155874 #14 Dec 28 2018 11:55:13
%S A155874 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 A155874 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 A155874 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 A155874 Smallest positive composite number such that a(n)+n is also composite.
%C A155874 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 A155874 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 A155874 Charlie Neder, <a href="/A155874/b155874.txt">Table of n, a(n) for n = 0..1000</a>
%F A155874 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 A155874 (PARI) a(n) = {forcomposite(k=4, 10, if (!isprime(k+n), return(k)););} \\ _Michel Marcus_, Dec 28 2018
%Y A155874 Cf. A122984.
%K A155874 easy,nonn
%O A155874 0,1
%A A155874 _Eric Angelini_, Jan 29 2009
%E A155874 More terms from _Charlie Neder_, Dec 28 2018