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%I #18 Sep 08 2022 08:45:19
%S 3,27,51,57,71,81,83,87,93,99,107,137,141,173,207,209,213,237,251,257,
%T 303,311,333,341,393,417,443,447,461,473,477,489,491,509,513,521,527,
%U 531,549,557,579,591,593,603,621,627,683,701,711,713,731,737,747,759
%N Numbers n such that the string 3731n is the decimal expansion of a prime number.
%C 31 and 37 are primes.
%H Harvey P. Dale, <a href="/A108114/b108114.txt">Table of n, a(n) for n = 1..1000</a>
%e 3 is in the sequence because 37313 is prime.
%e 99 is in the sequence because 373199 is prime.
%e 207 is in the sequence because 3731207 is prime.
%p a:=proc(n) local z: z:=nops(convert(n,base,10)): if isprime(3731*10^z+n)=true then n else fi end: seq(a(n),n=1..1000); # _Emeric Deutsch_, Jul 04 2005
%t Select[Range[1000],PrimeQ[3731*10^IntegerLength[#]+#]&] (* _Harvey P. Dale_, Aug 26 2013 *)
%o (Magma) [ n: n in [1..800] | IsPrime(Seqint(Intseq(n) cat [1, 3, 7, 3])) ];
%K nonn,base
%O 1,1
%A _Parthasarathy Nambi_, Jun 25 2005
%E More terms from _Emeric Deutsch_, Jul 04 2005
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