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%I #16 Sep 08 2022 08:45:19
%S 1,19,37,53,59,61,73,79,89,91,103,107,109,137,161,169,173,179,191,221,
%T 239,271,293,301,337,343,347,359,361,373,377,383,403,413,431,449,457,
%U 463,467,491,499,509,523,529,533,541,553,569,571,587,593,601,617,629
%N Numbers n such that the string 66n is prime.
%H Vincenzo Librandi, <a href="/A109639/b109639.txt">Table of n, a(n) for n = 1..2000</a>
%e If n=1 then 66n = 661 which is a prime.
%e If n=91 then 66n = 6691 which is a prime.
%p a:= proc(n) local k; for k from 1 +`if`(n=1, 0, a(n-1))
%p while not isprime(parse(""||66||k)) do od; a(n):=k
%p end:
%p seq(a(n), n=1..100); # _Alois P. Heinz_, Jul 30 2014
%t Select[Range[700], PrimeQ[66 10^IntegerLength[#] + #] &] (* _Vincenzo Librandi_, Jul 30 2014 *)
%o (Magma) [n: n in [1..600] | IsPrime(Seqint(Intseq(n) cat [6, 6])) ]; // _Vincenzo Librandi_, Jul 30 2014
%K nonn
%O 1,2
%A _Parthasarathy Nambi_, Aug 30 2005
%E More terms from _Vincenzo Librandi_, Mar 27 2010
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