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 A309329 Median of primes with n decimal digits. 4

%I

%S 4,47,509,5273,53047,532887,5356259,53765483,539119753,5402600081,

%T 54118210435,541947386821,5425907665571,54313871643797,

%U 543611236251491,5440228524355329,54438462600610510,544705097744731559,5449909581264135103

%N Median of primes with n decimal digits.

%C The number of n-digit primes < a(n) equals the number of n-digit primes > a(n). The median of an even number of values is understood to be defined as the arithmetic mean of the two central elements.

%F a(n) = (prime(A006880(n-1) + ceiling(A006879(n)/2)) + prime(A006880(n-1) + floor(A006879(n)/2) + 1)) / 2.

%e a(1) = 4 because {2, 3, 5, 7} are the 4 one-digit primes. The 2 central elements of the sorted list are 3 and 5. 4 = (3 + 5)/2.

%e a(2) = 47 because it is the central element of the sorted list of the A006879(2) = 21 two-digit primes. There are 10 such primes < 47 and 10 such primes > 47.

%Y Cf. A006879, A006880, A309359

%K nonn,base,more

%O 1,1

%A _Hugo Pfoertner_, Jul 25 2019

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Last modified May 26 12:47 EDT 2022. Contains 354091 sequences. (Running on oeis4.)