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 A089730 #3 Mar 30 2012 18:50:42
%S A089730 0,1,3,5,3,11,7,17,7,13,29,17,19,41,17,23,23,59,31,29,71,37,23,43,47,
%T A089730 47,101,47,107,53,61,59,67,137,73,149,73,79,53,83,83,179,89,191,97,
%U A089730 197,103,109,107,227,113,113,239,107,127,113,131,269,137,139,281,137
%N A089730 Greatest prime factor of all differences prime(n)-q, q prime and q<prime(n); a(1)=0.
%e A089730 n=10, prime(n)=29: a(10) = Max(Union(Factors(29-prime(i)):i<10)) = Max(Factors(27) u Factors(26) u Factors(24) u Factors(22) u Factors(18) u Factors(16) u Factors(12) u Factors(10) u Factors(6)) = Max({3} u {2,13} u {2,3} u {2,11} u {2,3} u {2} u {2,3} u {2,5} u {2,3}) = Max{2,3,5,11,13} = 13.
%Y A089730 Cf. A000040, A030173, A006530.
%K A089730 nonn
%O A089730 1,3
%A A089730 _Reinhard Zumkeller_, Jan 07 2004