A387500 Median of twin prime pairs with n decimal digits.

5, 36, 420, 4644, 51060, 518238, 5206320, 52565169, 528113445, 5302625562

Offset: 1

Author

Hugo Pfoertner, Sep 02 2025

Keywords

• nonn
• base
• more
• new

Comments

It is assumed that a pair of twin primes is characterized by its mean. The median of an even number of values is taken as the arithmetic mean of the two central elements in their sorted list.

Examples

			a(1): 2 pairs {3,5}, {5,7}, median = mean of {4,6} = 5;
a(2): 6 pairs {11,13}, {17,19}, {29,31}, {41,43}, {59,61}, {71,73}, median = mean of {30,42} = 36.
		

Crossrefs

Cf. A001097, A007508, A309329.

Programs

Mathematica

a[n_]:=Module[{s={},p=NextPrime[10^(n-1)]},While[p<10^n-4,If[PrimeQ[p+2],AppendTo[s,p+1]];p=NextPrime[p]];Median[s]];Array[a,7] (* James C. McMahon, Sep 02 2025 *)