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A062353 Primes of the form bbbbba... where a and b are digits. 3

%I

%S 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,

%T 97,113,223,227,229,331,337,443,449,557,661,773,881,883,887,991,997,

%U 1117,2221,3331,4441,4447,5557,6661,8887,11113,11117,11119,22229

%N Primes of the form bbbbba... where a and b are digits.

%C Number of terms of n digits: 4, 21, 16, 8, 9, 8, 2, 8, 7, 3, 4, 5, 2, 2, 4, 0, 3, 4, 2, 3, 2, 2, 4, 1, 0, ..., . - _Robert G. Wilson v_, May 29 2011

%H Charles R Greathouse IV, <a href="/A062353/b062353.txt">Table of n, a(n) for n = 1..260</a>

%e 4441 is a member where a=1 and b = 4.

%t f[n_] := Select[ Union@ Flatten@ Table[ FromDigits@ Join[ Table[b, {n - 1}], {a}], {b, 9}, {a, {1, 3, 7, 9}}], PrimeQ]; f[1] = {2, 3, 5, 7}; Array[f, 5] // Flatten (* _Robert G. Wilson v_, May 29 2011 *)

%o (PARI) print1("2, 3, 5, 7");for(n=2,20,forstep(k=10^n\9-1,10^n-9,10^n\9-1,for(m=k+1,k+9,if(isprime(m),print1(", "m))))) \\ _Charles R Greathouse IV_, May 29 2011

%Y Cf. A061022.

%K nonn,base,easy

%O 1,1

%A _Amarnath Murthy_, Jun 23 2001

%E More terms from _Jason Earls_, Jun 26 2001

%E Corrected and extended by _Dean Hickerson_, Jul 10 2001

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Last modified June 6 17:20 EDT 2020. Contains 334829 sequences. (Running on oeis4.)