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Exactly 3 digits from {1,2,3,4,5,6,7,8,9} can precede a term to form a prime.
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%I #11 Apr 06 2020 10:53:53

%S 13,21,23,29,33,37,43,49,51,59,61,69,71,79,81,93,99,101,103,111,113,

%T 121,127,133,137,161,163,167,171,179,181,211,213,219,253,257,259,269,

%U 271,277,281,287,293,301,307,309,319,329,333,337,343,347,349,351,361

%N Exactly 3 digits from {1,2,3,4,5,6,7,8,9} can precede a term to form a prime.

%H Daniel Starodubtsev, <a href="/A032693/b032693.txt">Table of n, a(n) for n = 1..10000</a>

%e For term 333, we find '2'333, '5'333 and '7'333 to be primes.

%o (Python)

%o from sympy import isprime

%o print([i for i in range(400) if [isprime(int(j + str(i))) for j in '123456789'].count(True) == 3]) # _Daniel Starodubtsev_, Apr 06 2020

%K nonn,base

%O 1,1

%A _Patrick De Geest_, May 15 1998