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 A099073 #18 Nov 25 2024 12:16:35
%S A099073 2,3,7,24,76,1100
%N A099073 Numbers k such that the concatenation of the first k-1 odd primes in decreasing order is prime.
%C A099073 A100003(n) = prime(a(n)). Next term is greater than 4500 and the prime corresponding to the next term has more than 21000 digits. Number of digits of primes corresponding to the six known terms of the sequence are respectively 1, 2, 9, 43, 198, and 4202. There is no known prime formed by concatenation of the first k odd primes in increasing order for 1 < k < 2250.
%C A099073 a(7) > 20000. - _Michael S. Branicky_, Nov 25 2024
%H A099073 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_008.htm">Puzzle 8. Primes by Listing</a>, The Prime Puzzles and Problems Connection.
%e A099073 7 is in the sequence because the first 6 odd primes are 3,5,7,11,13,17 and 17.13.11.7.5.3 is prime (dot between numbers means concatenation).
%t A099073 Do[If[PrimeQ[(v={};Do[v=Join[v, IntegerDigits[Prime[n-j+1]]], {j, n-1}];FromDigits[v])], Print[n]], {n, 2, 4500}]
%t A099073 Select[Range[1100],PrimeQ[FromDigits[Flatten[IntegerDigits/@ Reverse[ Prime[ Range[ 2,#]]]]]]&] (* _Harvey P. Dale_, Nov 12 2017 *)
%Y A099073 Cf. A046035, A099070, A099071.
%K A099073 base,more,nonn,nice
%O A099073 1,1
%A A099073 _Farideh Firoozbakht_, Nov 06 2004