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 A099070 #19 Nov 26 2024 02:14:11
%S A099070 4,5,6,7,8,9,26,1752,1753
%N A099070 Numbers k such that the concatenation of all nonprime natural numbers up to k with decreasing order is prime.
%C A099070 If k is in the sequence and k+1 is prime then k+1 is also in the sequence. Next term is greater than 5450 and the prime corresponding to the next term has more than 18000 digits. Number of digits of primes corresponding to the nine known terms of the sequence are respectively 2,2,3,3,4,5,29,5010 & 5010.
%C A099070 a(10) > 20000. - _Michael S. Branicky_, Nov 25 2024
%H A099070 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_008.htm">Puzzle 8. Primes by Listing</a>, The Prime Puzzles & Problems connection.
%e A099070 9 is in the sequence because all nonprime natural numbers up to 9 are 1,4,6,8 & 9 and 98641 is prime.
%t A099070 Do[If[PrimeQ[(v={};Do[If[ !PrimeQ[n+1-j], v=Join[v, IntegerDigits [n+1-j]]], {j, n}];FromDigits[v])], Print[n]], {n, 5450}]
%Y A099070 Cf. A046284, A099071.
%K A099070 base,more,nonn
%O A099070 1,1
%A A099070 _Farideh Firoozbakht_, Nov 04 2004