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 A256389 #6 Mar 28 2015 22:38:49 %S A256389 1,2,3,4,6,8,9,10,12,14,15,16,18,20,22,24,26,27,28,30,32,34,36,38,39, %T A256389 40,42,44,46,48,50,52,54,56,57,58,60,62,64,66,68,69,70,72,74,76,78,80, %U A256389 82,84,86,88,90,92,94,96,98,99,100,102,104,105,106,108,110 %N A256389 Numbers n such that one or more primes can be the arithmetic mean of 2 semiprimes whose difference is 2*n. %C A256389 That is, there are several primes p, such that p+n and p-n are both semiprime. %C A256389 Complement of A256387. %C A256389 The terms of this sequence that do not belong to A256388 are even. %e A256389 A256381 is the list of numbers n such that n-3 and n+3 are semiprimes, and it contains a single prime, hence 3 is in the sequence. %e A256389 A256382 is the list of numbers n such that n-4 and n+4 are semiprimes, and it contains several primes, hence 4 is in the sequence. %Y A256389 Cf. A124936, A105571, A256382. %Y A256389 Cf. A256387 (no prime), A256388 (a single prime). %K A256389 nonn %O A256389 1,2 %A A256389 _Michel Marcus_, Mar 27 2015