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 A099070 Numbers n such that the concatenation of all nonprime natural numbers up to n with decreasing order is prime. 3
 4, 5, 6, 7, 8, 9, 26, 1752, 1753 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If n is in the sequence and n+1 is prime then n+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. LINKS C. Rivera, Primes by Listing. EXAMPLE 9 is in the sequence because all nonprime natural numbers up to 9 are 1,4,6,8 & 9 and 98641 is prime. MATHEMATICA 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}] CROSSREFS Cf. A046284, A099071. Sequence in context: A123977 A109602 A084991 * A288658 A065342 A231369 Adjacent sequences:  A099067 A099068 A099069 * A099071 A099072 A099073 KEYWORD base,more,nonn AUTHOR Farideh Firoozbakht, Nov 04 2004 STATUS approved

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Last modified April 5 18:08 EDT 2020. Contains 333245 sequences. (Running on oeis4.)