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 A175532 #15 Oct 14 2024 02:58:28 %S A175532 1,9,13,25,133,193,18673,57313,1032313,4387273,3450430573,11717813053, %T A175532 21691948933 %N A175532 a(1) = 1; a(2) = 9; for n>2, a(n) = smallest number of the form 4k+1 and a(n) > a(n-1) such that the pairwise sums of elements are all semiprimes. %C A175532 Or, for i<>j, (a(i)+a(j))/2 are primes. %C A175532 Starting with a(5)=133 on all terms === 13 mod 20. %C A175532 Is this sequence finite? %Y A175532 Cf. A115760. %K A175532 nonn,more %O A175532 1,2 %A A175532 _Zak Seidov_, Jun 12 2010 %E A175532 a(11)-a(13) from _Jason Yuen_, Oct 13 2024