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 A280828 #38 Jan 14 2017 16:28:47 %S A280828 4,22,202 %N A280828 Numbers k of the form 2*10^m + 2 such that 10^k + 9 is prime. %C A280828 Let k=2*10^(n-1)+2, then a(n)=10^k+9. For all k>4, k is a term of A058441. %C A280828 The only known terms from A088275 (Numbers n such that 10^n + 9 is prime) that are of the form 2*10^j + 2 are 4, 22, and 202; given the lower bound given for that sequence's next term, a(4) >= 200002. - _Jon E. Schoenfield_, Jan 11 2017 %C A280828 For n<4, let k=a(n) and p=(10^k-9)/10^(k/2)+3=10^(k/2)+3, then p is prime. - _Sergey Pavlov_, Jan 13 2017 %F A280828 Numbers k of the form 2*10^m + 2 such that 10^k + 9 is prime. %e A280828 For n=1, a(1)=4 and 10^4 + 9 is prime. %Y A280828 Cf. A043037, A058441, A088275, A144249, A205529. %K A280828 nonn,hard,bref,more %O A280828 1,1 %A A280828 _Sergey Pavlov_, Jan 08 2017